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THE CALORIFIC POWER 
OF FUELS. 

FOUNDED ON 

SCHEURER-KESTNER'S 
POUVOIR CALORIFIQUE DES COMBUSTIBLES. 

WITH THE ADDITION OF 

A VERY FULL COLLECTION OF TABLES OF 

HEATS OF COMBUSTION OF FUELS, 

SOLID, LIQUID AND GASEOUS. 

TO WHICH IS ALSO APPENDED 

THE REPORT OF THE COMMITTEE ON BOILER TESTS 

OF THE AMERICAN SOCIETY OF MECHANICAL 

ENGINEERS (DECEMBER, 1897) ; TABLES 

OF CONSTANTS USED. 



/by 

HERMAN POOLE, F.C.S., 

Member of the Society of Chemical Industry ; the American Chemical Society , 

the American Society of Civil Engineers ; the American 

Society of Mechanical Engineers ; etc. 



FIRST EDITION 
FIRST THOUSAND. 



NEW YORK: 

JOHN WILEY & SONS. 

London: CHAPMAN & HALL, Limited. 

1898. 




2nd COPY, 
1898. 



w 



\* 



' ^ :<ri 



4359 



Copyright, 1898, 

BY 

HERMAN POOLE. 



£_ 4.101/ 



TO MY WIFE 

THIS BOOK IS AFFECTIONATELY 

DEDICATED. 



PREFACE. 



THE books on fuels hitherto published in English, contain 
only a few scattered facts regarding their calorific powers, how 
they are obtained, and the practical use made of them. Quite 
frequently these books are consulted for these facts, and the 
information they do contain is utilized to its fullest extent. 
It was thought that a book especially devoted to this subject 
containing all the reliable data might be of interest, and in 
furtherance of that idea this book is published. 

The work commenced as a translation of M. Scheurer-Kest- 
ner's "Pouvoir Calorifique des Combustibles "/ but changes be- 
came necessary to adapt it to American methods and data, 
and it was deemed advisable to simply use the skeleton of the 
work and fill it in, as considered best. Even this skeleton has 
hardly been preserved intact, as the arrangement of much of 
the material has been changed, many portions omitted, many 
new ones supplied, and in some of the original discussions the 
argument has been so changed as to point nearly opposite to 
that advocated by M. Scheurer-Kestner. 

The work embraces only that portion of calorimetric de- 
terminations having a bearing on fuel values. A concise 
description is given of the leading calorimeters, those most 
commonly used being described more fully than the others, and 
some examples of working and calculations are added. 

Coal being the principal fuel naturally receives more space 
than any of the others, and most of the examples and calcula- 
tions are based on results from this fuel. The other fuels are 



VI PREFA CE. 

discussed briefly, some space being given to the heats of for- 
mation of the different kinds of gas, and the advantages gained 
by their use. A short account of theoretical flame tempera- 
tures is given, with the methods of calculating and applying 
the same. 

The Report of the Committee on Boiler Tests, submitted 
to the American Society of Mechanical Engineers, in Decem- 
ber, 1897, is published in full, as are also several of the appen- 
dices to the report. This report revises the old method of 
1885, and gives the most recent methods of testing boilers 
and reporting the same. 

A set of tables of constants used in this and allied sub- 
jects is given, and finally a collection of calorimetric and ana- 
lytic data on all the kinds of fuel used. It is believed that these 
tables are fuller and more complete than any previously pub- 
lished in any language, and in collating them all available books 
and periodicals have been freely used. In all instances where 
the author was known, he has been credited with his results. 
Of course in such a large amount some unreliable data may 
have crept in, but all possible pains have been taken to exclude 
any such. The list of periodicals, etc., consulted will be found 
following the table of contents. 

For help in the work, and especially the tabular matter, the 
author is under obligations to many. Prominent among them 
are Profs. R. C. Carpenter, E. E. Slosson, W. O. Atwater, 
and D. S. Jacobus; and Messrs. William Kent, R. S. Hale, 
F. L. Slocum, W. B. Day, and C. E. Emery. The Astor 
Library and the Libraries of the American Society of Civil 
Engineers and the American Society of Mechanical Engineers 
were freely used, and much help obtained from the librarians. 
Most of the cuts are from Scheurer-Kestner's book; a few 
were taken from Lunge and Hurter's Alkali-Maker's Hand- 
book ; some from Groves and Thorpe's work on Fuels ; a 
few from the Reports of the American Society of Mechanical 
Engineers; two from Dingler's Polytechnic Journal; one 



PREFA CE. Vll 

from the Scientific American Supplement ; and one from 
Engineering News. 

The work has been unavoidably delayed waiting for de- 
sired data, some of which came too late to be used. 

The author knows well that the book is far from perfect 
or complete, but it is as near so as could be made with the 
diverse kinds of material obtainable. Some errors, especially 
in the tables, may be found, which he hopes to correct in the 
future. 

That it may be found of service and aid to others in their 
work on fuels is the sincere wish of the author. 

HERMAN POOLE. 

New York, Jan. i, 1898. 



CONTENTS. 



PAGE 

Preface v 

Contents i x 

Authorities . . » xiii 



CHAPTER I. 

Fuels i 

Definitions. Fuels. Calorific Value. Heat of Combustion. 
Thermometers. Metastatic Thermometers. 

CHAPTER II. 

Method of Determining Heat of Combustion 7 

Methods Depending on the Composition. On the Reducing 
Power. 

CHAPTER III. 

Calorimeters 12 

Installation. Evaluation in Water. Correction for Readings. 

CHAPTER IV. 

Calorimeters with Constant Pressure 20 

Calorimeters using Air or Oxygen. Favre and Silbermann's. 
Alexejew's. Fischer's. Thomsen's. Carpenter's. Schwack- 
hofer's. W. Thompson's. Barrus's. Hartley and Junker's. 

CHAPTER V. 

Calorimeters with Constant Volume 45 

Relation of Constant Volume and Constant Pressure. An- 
drews'. Berthelot's. Description. Working. Calculation. 



X CONTENTS. 

CHAPTER VI. 

PAGE 

Mahler's Bomb 57 

Description. Working. Calculation. Examples ; Colza Oil, 
Coal, Gas, Coke. Atwater's. Kroeker's. Walther-Hempel. 
Witz's. 

CHAPTER VII. 

Solid Fuels 75 

Coal. Lignite. Peat. Coke. Charcoal. Wood. 

CHAPTER VIII. 

Liquid Fuels 88 

Shale Oils. Petroleum. 

CHAPTER IX. 

Gaseous Fuels 92 

Heat of Combustion from Analysis. Coal Gas. Gas of Gaso- 
genes. Producer or Air Gas. Water and Mixed Gas. Natural 
Gas. 

CHAPTER X. 

Calorific Power of Coal burnt under a Steam-boiler 109 

Distribution of Heat. Weight of Fuel. Sampling the Fuel. 
Analysis of the Coal. Analysis of the Cinders. Duration of the 
Test. The Water Evaporated. Temperature of the Steam. 
Moisture of Steam. Corrections for Quality of Steam. Quality 
of Superheated Steam. 

CHAPTER XI. 

Calorific Power of Coal burnt under a Steam-boiler — Con- 
tinued. Air Supplied and Waste Gases 125 

Volume of Air Necessary to Combustion. Volume of Waste 
gases by Analysis. Gas Sampler. Analysis of Gases. Calcula- 
tion of Volume from Analysis. Calculation of Volume of Air 
Supplied. Calculation of Weight of Waste Gases from Analysis. 
Volume of Waste Gases by the Anemometer. Fletcher's Ane- 
mometer. Segur's Differential Gauge. Hirn's Method. Dasym- 
eter. Econometer. Gas Composimeter. Temperature of Waste 
Gases. Pneumatic Pyrometer. Carbon in Smoke. 



CONTENTS. Xi 



CHAPTER XII. 

PAGE 

Calorific Power of Coal burnt under a Steam-boiler — Con- 
tinued. Calculation of the Heat Units 159 

Heat of Aqueous Vapor. Heat of Waste Gases. Heat of the 
Temperature. Heat of the Hygroscopic and Combustion Water. 
Calories of the Combustible Gases. Calories due to Soot. Dis- 
tribution of Calories — Loss. 

Flame and Flame Temperatures 168 

Weight and Heat Units of Carbon Vapor 173 

Evaporative Power of Fuel 174 



APPENDIX. 

Report of the Committee on the Revision of the Society Code 
of 1885, Relative to a Standard Method of Conducting Steam- 
boiler Trials 177 

Report of Committee. Rules for Conducting Trial. Form for 
Report. 

Tables 198 

Fuel Tables 209 

Index. 249 



AUTHORITIES CONSULTED. 



The following list contains the names of the different pub- 
lications consulted to obtain data, especially for the tables. 
Dates are not usually given, as in many cases the entire file 
was used since 1868. 

Alkali Reports, England. 

American Engineer. 

American Gas Light Journal. 

American Manufacturer. 

Annalen der Chemie und Physik. 

Annales de Chimie et Physique. 

Annales des Mines. 

Australian Mining Standard. 

Bayerisches Industrie und Gewerbeblatter. 

Bell, Sir I. L., Chemical Phenomena of Iron-smelting. 

Berichte der Deutscher Chemischer Gesellschaft. 

Berthelot, Essai de Mecanique Chimique. 

Berthier, Traite des Essais par la Voie seche. 

Bulletin No. 21, U. S. Dept. Agriculture. 

" University of Wyoming. 

" de la Societe Industrielle de Mulhouse. 

" de la Societe Chimique de Paris. 

" de l'Association des Proprietaires d'Appareils a Vapeur du 
Nord de la France. 
Chemical News. 
Colliery Guardian. 

Comptes Rendus de l'Academie des Sciences. 
Crookes and Rohrig, Metallurgy. 
Dingler's Polytechnisches Journal. 
Dufrenoy, Traite de Mineralogie. 
Electrical Engineering. 

xiii 



XIV AUTHORITIES CONSULTED. 

Engineer. 

Engineering. 

Engineering and Mining Journal. 

Engineering Mechanics. 

Engineering News. 

Groves and Thorpe, Chemical Technology, Vol. I. 

Gliickauf. 

Ice and Refrigeration. 

Iron Age. 

Isherwood, B. M., Engineering Precedents. 

" " Researches in Steam Engineering. 

Jahrbuch der K. K. Berg-Akademie. 

fur Geologic 
Johnson, W. B., Report to Congress, U. S. A., 1844. 
Journal American Chemical Society. 

Canadian Mining Institute. 

Chemical Society. 

Franklin Institute. 

Society of Chemical Industry. 

Imperial Institute. 

Iron and Steel Institute. 

de l'Eclairage au Gaz. 

des Usines a Gaz. 

du Gaz et de l'Electricite. 

fur Gasbeleuchtung. 

fur Praktische Chemie. 

fur Angewandte Chemie. 

of Gas Lighting. 
Kent, William, Pocket-book. 
Le Genie Civil. 

Memoires de la Societe des Ingenieurs Civils. 
Mineral Industry, Vol. I. 

Mineral Resources, U. S. A., various volumes. 
Mining Journal. 

Morin and Tresca, Machines a Vapeur. 
Oesterreichische Zeitschrift fur Berg- und Hiittenwesen. 
Peclet, Traite de la Chaleur. 
Percy's Metallurgy, Fuels. 
Philosophical Magazine. 
Polytechnisches Centralblatt. 
Progressive Age. 

Proceedings : Alabama Industrial and Scientific Society. 
" American Gaslight Association. 



AUTHORITIES CONSULTED. XV 

Proceedings: American Institute Mining Engineers. 
" American Society of Civil Engineers. 

" Institute of Mechanical Engineers. 

" Institution of Civil Engineers. 

Reports : British Alkali Commission. 

" British Association of Gas Managers. 

" Bureau of Mines, Canada. 

Department of Mines, New South Wales. 
" Geological Survey, Ohio. 

" Geological Survey, U. S. 

South Lancashire and Cheshire Coal Association on Boilers 
and Smoke Prevention, 1869. 
Revista Minera. 
Revue Scientifique et Industrielle. 

Universelle des Mines. 
Sanitary Engineer. 
Scheerer, Lehrbuch der Metallurgie. 
Scheurer-Kestner, Pouvoir Calorifique des Combustibles. 
Science. 

Ser, Traite de Physique Industrielle. 
Stahl und Eisen. 
Stevens Indicator. 
Thomsen, Thermo-chemie. 
Transactions Newcastle Chemical Society. 
Ure's Dictionary. 

United States Census Bulletin, 1890. 
Williams, C. W., Fuel, its Character and Economy. 
Watt's Dictionary of Chemistry. 

Witz, Traite theorique et pratique des moteurs a gaz. 
Wurtz, Dictionnaire de Chimie. 
Zeitschrift Physikalische Chemie. 

" des Vereines Deutscher Ingenieure. 

Zeitung Berg- und Hiittenwesen. 



CALORIFIC POWER OF FUELS 



CHAPTER I. 
INTRODUCTORY. 

FUELS. 

FUELS are those substances containing carbon, or carbon 
and hydrogen, which are utilized for the heat they produce 
upon union with oxygen. The products of this union, called 
combustion, are carbonic acid or carbonic acid and water. 
Many fuels, such as wood, peat, crude petroleum, etc., exist 
naturally; others, such as coke, charcoal, coal-gas, etc., are 
formed artificially. 

The fuel par excellence to-day is coal. Improvements in 
transportation allow deliveries at points more and more 
remote from the mines, and the increasing demand, aided by 
new and improved machinery, tends to lower the cost. New 
locations are still being discovered, and the old ones are being 
worked more thoroughly and completely. A large portion of 
this book will be devoted to coal, other fuels being treated 
incidentally; and such treatment is fitting, since it is the study 
of coal to which the energies of physicists and engineers are 
still principally devoted in their researches on the calorific 
power of fuel. 

For convenience of discussion the fuels will be divided 
into three general heads: 

Solid fuels — coal, lignite, peat, coke, charcoal, and wood. 



2 CALORIFIC POWER OF FUELS. 

Liquid fuels — petroleum, shale oils, vegetable and animal 
oils. 

Gaseous fuels — coal gas, producer gas, water gas, mixed 
gas, natural gas. 

CALORIFIC POWER OR HEAT VALUE. 

The quantity of heat generated by the combustion of 
a definite quantity of fuel in oxygen is called the calorific 
power, heat value, or heat of combustion. 

The expression calorific power or heat value has a wider 
signification than heat of combustion. In the popular sense 
the former ones apply to the measure of an industrial yield as 
well as to the heat given off by the fuel during its complete 
combustion. The expression heat of combustion, more nearly 
correct from a scientific point of view, is applied, on the con- 
trary, only to that quantity of heat generated by the substance 
when completely burnt; that is to say, when the carbon and 
hydrogen are completely changed to carbonic acid and water. 
The unit adopted for these quantities of heat is the Calorie 
and the British Thermal Unit. 

The Calorie is the quantity of heat absorbed by the unit of 
weight of pure water when its temperature is increased one 
degree Centigrade. This unit is usually one gram or one 
kilogram. When it represents the atomic or molecular 
weight, it is called the atomic or molecular calorie, the gram 
being taken as the atomic unity. 

The British Thermal Unit (B. T. U.) is the quantity of 
heat absorbed by one unit (usually one pound) when its tem- 
perature is increased one degree Fahrenheit. It is -^ of a 
calorie. 

A kilogram in burning generates n calories with a kilogram 
as unit and the Centigrade scale; a pound generates n calories 
with a pound as unit and the Centigrade scale (W. Kent's 
pound-calorie) ; or, whatever the weight taken, there will be 
generated the same number of calories, using the same unit of 



INTRO D UCTOR Y. 3 

weight and the Centigrade scale. Hence to pass from the 
Centigrade scale to the Fahrenheit scale multiply by the 
factor 1.8, that being the ratio of the two scales. 

In this work calories referred to the kilogram (kilo- 
calories) will be used, and the calorie will be the quantity of 
heat necessary to raise the temperature of that amount of pure 
water one degree Centigrade. We will omit consideration of 
the variations in specific heat of water; to consider these it 
would be necessary to state that the initial temperature was 
0° C. But, as remarked by Berth elot, " the calorie varies 
only to a very slight degree if we take the water at a slightly 
increased temperature — at 1 5° or 20 , for example ; so that we 
are accustomed to regard as constant the specific heat absorbed 
by the water for each degree comprised in this interval of 
temperature, thus simplifying the calculations." We may 
lessen this little error by referring the calorie to a litre of 
water instead of a kilogram, that is, by measuring the water 
instead of weighing it ; the weight of a litre of water diminish- 
ing from its maximum density at 4 C, while its specific heat 
gradually increases. The error of calculation is thus made 
less than the error of experiment. 

HEAT OF COMBUSTION. 

When the fuel contains hydrogen, its heat of combustion 
may be expressed in two ways. Hydrogen in burning pro- 
duces water, and this water may be either condensed or in the 
state of vapor. The same number does not apply to both 
cases, since the vaporization of the water formed consumes 
heat, which is not given up to the calorimetric bath. We 
usually consider the heat of combustion, the result of the 
experiment made under ordinary conditions, or when the 
water is in the liquid state; this is the general acceptance of 
the term heat of combustion. Some authors, however, prefer 
to consider the water as vapor. 

It is easy, however, to change from one system to the 



4 CALORIFIC POWER OF FUELS. 

other. The heat of combustion of one kilogram of hydrogen 
being 34500 calories,* and the water formed being liquid at 
o° C, a portion of the 34500 calories is used to vaporize the 
water in the case where it is gaseous or considered as such. 

Experiment has shown that the heat of vaporization of 
water is expressed by the formula of Regnault, 

606.5 -|- 0.305/, or 

1091.7 -f- o.305(/ — 32 ) for Fahrenheit degrees, 

in which t represents the temperature of the water in the state 
of vapor. Now one kilogram of hydrogen produces nine 
kilograms of water. To keep these nine kilograms of water 
in vapor, at ioo° C. for example, there will be needed, by the 
above formula, 637 calories per kilogram of water, or nine 
times as much per kilogram of hydrogen, which is 5733 
calories. These 5733 calories reduce to 5453 when the water 
is considered as being at o° C. instead of at ioo° C. Deduct- 
ing 5453 calories from 34500 calories representing the heat of 
combustion of hydrogen, the water formed being condensed, 
we obtain 29047, which number represents the heat of com- 
bustion of hydrogen, the water being in the state of vapor 
at o c . We will call it, in round numbers, 29100! calories, as 
is done by several writers. 

THERMOMETERS. 

Before taking up the study of calorimeters, we must con- 
sider the calorimetric thermometer, which is a most important 
part of the apparatus employed. The reading of the ther- 
mometer and the corrections are quite delicate and also very 
important, the calculation of the heat of combustion depend- 
ing principally on their accuracy. 

In this work calorimetric questions relating to fuel only 
will be considered; hence a description of ordinary ther- 

* 62100 B. T. U. \ 52380 B. T. U. 



IN TROD UCTOR Y. 



5 



mometers and their manufacture will not be needed. They 
are usually bought all finished, and should be obtained only 
from reliable dealers. 

Favre and Silbermann employed a thermometer of their 
own design, divided into ^ degrees and graduated from 32 
to o° C. Each degree occupied about 0.3 inch. By means 
of a cathetometer they read to -j-J-g- of a degree. Their calori- 
metric bath of 2 litres capacity was subjected to at least 8° 
elevation in temperature, and the quantity of substance 
necessary to use at times exceeded 2 ^ • 2 

grams. To lessen this amount of rise 
in temperature and also the time of 
combustion, they used longer thermo- 
meters, with scales reading to j^° or "' 
Scheurer-Kestner used — 



even to two' 



cu 



1 



& 



a thermometer divided to -^q° with his 
Favre and Silbermann calorimeter. 
Since then they have been used gener- 
ally. Such thermometers are difficult 
to work with, and require care in ma- 
nipulation, and often a series of ther- 
mometers or at least two with scales 
in sequence are employed. If the 
initial temperature of a calorimetric 
bath is found a little above the highest 
graduation on the first thermometer, 
and if the rise in temperature of the 
bath amounts to two degrees, we must 

substitute the second one having for its lowest degree the 
highest of the first. Besides the trouble of substitution, it 
necessitates a correction for agreement of the degrees common 
to the two instruments. To obviate this difficulty the 
"metastatic" thermometer was invented by Walferdin and 
described in the Comptes Rendus de V ' A cade mi e des Sciences, 
1840, p. 292, and 1842, p. 63. 



Fig. 1. — Metastatic 
Thermometer. 



O CALORIFIC POWER OF FUELS. 

The metastatic thermometer is a differential thermometer 
with a variable scale. At will, a certain quantity of mercury 
flows into the bulb. By this means we raise or lower the 
degrees for which it may be used. Suppose an ordinary 
thermometer graduated from o° to io°, and left open at 
the top at the ioth degree. If we wish to use it between \2° 
and 14 , heat it to 14 , and a portion of mercury correspond- 
ing to 4 escapes. Now, instead of showing a difference of io° 
between o° and io°, it will show this difference between 4 
and 8°, the original o° having descended to — 4 . It will be 
similar for temperatures of io°, 20 , or 30 , as desired. By 
closing the thermometer at the top instead of leaving it open, 
and blowing a bulb in the upper portion as overflow, the 
conditions will remain the same. The thermometer has now 
become metastatic. These thermometers are made by Baudin 
of Paris, from whom full directions for use and corrections can 
be obtained. 

With all thermometers it is essential that the glass of the 
bulb should be rather thin, or the thermometer will be " too 
slow." The slightest difference in temperature must be 
shown immediately by a movement of the mercurial column. 
To test for sensibility, read the height of the column and then 
place the hand on the bulb. If sufficiently sensitive the mer- 
cury will descend quickly from the expansion of the glass and 
afterwards rise. In thermometers divided to t ±-q° this move- 
ment should be immediate, and over several hundredths. 

In ordinary calorimetric experiments the correction due to 
length of the mercury column flowing out of the bulb may 
be neglected for several reasons; the experiments should be 
made in a room where the temperature is nearly the same as 
that of the calorimetric bath, such correction would be of 
very little consequence for a slight change of temperature, 
and the experimenter should plunge the thermometer into the 
bath as deep as is necessary to take the reading at the level 
of the eye. 



CHAPTER II. 

METHODS OF DETERMINING HEAT OF COMBUSTION. 

THERE are two methods for determining tne heat of com- 
bustion of substances — one by calculation based on the 
chemical composition, and the other by actual combustion in 
a calorimeter. The first method may be considered under 
two heads: that in which the units are calculated directly from 
the composition, and that in which they are calculated from 
the quantity of oxygen consumed during combustion in a 
crucible. 

CALCULATION FROM CHEMICAL COMPOSITION. 

Dulong stated that the heat generated by a fuel during 
combustion was equal to the sum of the possible heats gener- 
ated by its component elements, less that portion of the hy- 
drogen which might form water with the oxygen of the fuel. 

His formula was 

x = 8080C + 34500 (h - °), 
or expressed in B. T. U.'s, 

x = 14500C -f- 62 100 (H — —J, 

in which 

x = the heat of combustion sought; 
8080 = the heat of combustion of carbon in calories ; 
14500 = " " " " " " " B. T. U. ; 

34500= " " " " " hydrogen in calories ; 

62100 = " " " " " " " B. T. U. ; 

7 



5 CALORIFIC POWER OF FUELS. 

H — — = the quantity of hydrogen less that supposed to form 
water with the oxygen. 

Other authors and experimenters have tried to interpret 
their results by a general formula with varying success. 
Many of them by working on a certain number of coals from 
a certain location work out a formula which applies to that 
set of coals, but not as well to another set. A few of them 
will be given. They all resemble Dulong's and are usually 
only modifications of his original one. 

The Verein Deutscher Ingenieure adopted the following: 

x = 8100C -f- 29000 f H — o~J + 2 5°°S — 6ooii, 

in which allowance is made for the heat of combustion of 
sulphur and the heat of the hygroscopic water. All the 
coefficients are round numbers and that for hydrogen, 29000, 
is the one in which the water is supposed to be as aqueous 
vapor, all the water being considered as passing off in that 
state. None of the other formulae uses this coefficient. 
It gives rather low results. The question as to the advis- 
ability of reckoning the heat due to sulphur is a debatable 
one. In no case does it amount to more than a verv small 
per cent and can have but little effect on the total. 
Balling gives as formula 

x = 8080C + 34462 (h - 0) - 652(£ + 9H) 

to represent the actual occurrences in a steam-boiler fire work- 
ing under a pressure of steam corresponding to 300 F. 

Schwackhoefer.made the following modification to allow 
for the correction due to hygroscopic water: 

x = 8080C + 34500 (h - 5) - 637^. 



METHODS OF DETERMINING HEAT OF COMBUSTION. 9 

Mahler formulated one based on the results of calorimetric 
determination of the heat of combustion of 44 different kinds 
of fuel. It is 



x 



8140C + 34500H — 3 000 (0 + N) m 
100 



or simplified, 

x = 111.4C+ 375H — 3000; 
or in B. T. U.'s, 

x = 200. 5 C + 675 H — 5400. 

With the coals he examined he found a very close agree- 
ment between the results calculated by this formula and 
those observed. A similar but not equally close concordance 
was found using the Dulong formula. With wood and lig. 
nites the difference amounted to 2 per cent. His formula 
applies also to other substances whose constituents are accu- 
rately known. Cellulose, the heat of combustion of which 
according to Berthelot is 4200 calories, by Mahler's formula 
is 4264. 

In summing up he says: " From a scientific point of 
view, in the present state of our knowledge on the subject, 
we cannot give a general formula depending strictly on the 
chemical composition which will give the calorific power of 
combustibles, substances so complex and varied." 

Lord and Haas in a paper read before the American Insti- 
tute of Mining Engineers, Feb. 1897, state that in a series of 
forty Pennsylvania and Ohio coals they found differences 
varying from -f- 2.0 to — 1.8 per cent between the calculated 
and the observed results, and an average difference of — 0.12 
per cent. 

In 1896 Bunte published some analyses and calorimetric 
tests of gas-cokes, showing a difference of from -f- 0.04 to 
— 1.2 per cent. 



IO CALORIFIC POWER OF FUELS. 

Three elements enter into these cases, the analysis, the 
calculation, and the combustion; all may be erroneous. As 
the matter stands now the weight of error seems to be on the 
side of the analysis, as our methods of analysis, especially in 
water determinations, are not entirely satisfactory; yet it must 
be confessed that some of the most recent analyses give a 
basis trom which very close agreement can be calculated. 
With such fuels as coke, charcoal, or anthracite, having but 
little volatile matter, the results agree quite well, but with the 
bituminous coals, asphalts, mineral oils, etc., which are so 
very complex, the differences are greater.* In these the 
actual proximate chemical constitution seems to make a differ- 
ence. It may be safely stated, however, that for ordinary 
industrial uses, in absence of the possibility of a calorimetric 
test, and with coals having under 20 per cent of volatile 
matter, a fairly accurate approximation may be arrived at by 
calculation. 

The great inducement that formerly existed in favor of 
calculated results exists no longer. I refer to the difficulty 
of making a calorimetric test. These can be made now by 
means of the modern apparatus, so simple and almost self- 
regulating that the time consumed is but a small fraction of 
that needed for an analysis, and the labor and care, hardly 
anything in comparison. 

If possible, by all means have a calorimetric test. If not 
possible, use the best analysis available. 

CALCULATION FROM QUANTITY OF OXYGEN USED. 

This is the litharge reduction test. It depends on 
Welter's formula, which is based on the hypothesis that the 
heat of combustion is proportional to the quantity of oxygen 
consumed: 

N = mP, 

* Mahler's limit for Dulong's formula is O -f N > 15. 



METHODS OF DETERMINING HEAT OF COMBUSTION. II 

in which N is the heat of combustion sought, m is the coeffi- 
cient previously determined, and P is the weight of oxygen 
necessary for the combustion of one kilogram of the substance. 
Giving P the value resulting from the use of the equiva- 
lents — 1 6 for oxygen to burn 6 of carbon, and 8 for oxygen 
to burn I of hydrogen — we have 



^C + 8H = 8(£ + h); 



>3 
and the general formula becomes 

N = Sm (- + h) = 26880 (- + h). 

To use this method the combustible is mixed with an 
excess of litharge and heated in a crucible. The button of 
lead formed shows the amount of oxygen consumed, and from 
this is deduced the heat by means of the formula. The heat 
should be increased very slowly. Mitchell substituted white 
lead for litharge and claimed to obtain uniform results. 

This formula was recommended by Berthier, and has been 
used since by a few others. It is faulty, as was shown by 
some of Berthier's own determinations in which contradictory 
results were obtained. Dr. Ure showed that no uniform re- 
sults could be obtained using the same materials. Scheurer- 
Kestner in 1892 showed that the formula not only gave erro- 
neous results, but actually reversed the relation of combus- 
tibles. In one case cited the heats actually obtained by a 
calorimeter were 8813 and 8750, while by the litharge test 
they were 7547 and 7977. The results were not only low, 
but reversed the ratio. 

This method is allowable only in cases where the crudest 
approximations are desired and where no analyses or calori- 
metric tests can possibly be made. 



CHAPTER III. 
CALORIMETRY. 

Calorimeters for rapid combustion are invariably com- 
posed of a combustion-chamber and a calorimetric bath, 
usually a cylinder, surrounding it and containing a known 
quantity of water, the elevation in temperature of which is 
measured. The combustion is made in oxygen, pure or 
diluted. 

Combustion-chambers are either under a constant pressure, 
as in the calorimeters of Rumford, Favre and Silbermann, 
etc. ; or with a constant volume, as in the calorimeters of 
Andrews, Berthelot, etc. With solids the difference of results 
obtained under constant volume and constant pressure is so 
small that we shall not consider it. With gases, however, it 
is different, and we will state under which conditions the 
results have been obtained. 

The first calorimetric experiments date from Lavoisier and 
Laplace. In 1814 Count Rumford replaced the ice calorim- 
eter of Lavoisier by an apparatus in which the heat devel- 
oped during the combustion was absorbed by water. It was 
some time after, 1858, that Favre and Silbermann discovered 
the causes of the great errors of their predecessors, and pub- 
lished methods for correcting some while avoiding others. 
We owe to them, above all, the observation that, even when 
supplied with pure oxygen, combustion may be only partial, 
on account of the formation of combustible gases. They 
determined that this occurs generally, and gave a method of 
estimating the unburnt gases, so as to make allowances in the 
calculation. 

12 



CALO RIME TRY. I 3 

Carbon, which, before their time, had given only 7624 
calories to Laplace, 7386 to Clement-Desormes, 7915 to Des- 
pretz, 7295 to Dulong, and 7678 to Andrews, yielded to F. 
& S. 8081 after correction for carbonic oxide in the waste 
gases. This number has since been increased to 8140 by the 
latest determinations of Berthelot. Berthelot and Vielle have 
shown that by using oxygen under pressure complete com- 
bustion can be attained. 

INSTALLATION OF APPARATUS. 

The apparatus should be placed in a room free from 
sudden changes in temperature and consequently protected 
from direct sunlight. If it is not entirely protected from 
solar radiation, the apparatus may be set up on the north 
side and shaded from the direct midday sun by a screen. 

The calorimeter cylinder with its accessories, as well as the 
distilled water used, should remain in the room long enough 
to acquire its proper temperature. The cylinder should be 
protected as much as possible from radiation by envelopes 
which vary according to circumstances. Favre and Silber- 
mann used a cylinder with a double wall. The external one 
was filled with water, and between this one and the cylinder 
proper swan's down was packed. The upper part of the 
cylinder also had a layer of thick paper covered with down 
on the under side. 

Berthelot states that the down is more troublesome than 
useful, and that it may be omitted with advantage. The space 
between the cylinder and its envelope forms a layer of air 
which is an excellent non-conductor. In modern instruments 
the down is replaced by a thick layer of felt. Berthelot even 
omits this covering, stating that the great cause of loss of 
heat was not from radiation, but due to evaporation produced 
by the agitation of the water in contact with the air. He 
surrounds his cylinder with a layer of air inside of the 
envelope of water, and outside of all a layer of felt 0.8 inch 
thick. By this means external influence is much reduced. 



14 CALORIFIC POWER OF FUELS. 

EVALUATION OF THE CALORIMETER IN WATER. 

Before using a calorimeter its equivalent in water must be 
determined; that is, we must calculate to what quantity of 
water it corresponds in terms of specific heat. This is to 
be added to the weight of water employed and includes the 
combustion-chamber, cylinder, and the immersed pieces, 
thermometer, supports, etc. 

Below is given an example showing the calculation of the 
value in water of a Favre and Silbermann's calorimeter: 

Copper, 1145.651 grams at 0.09516 specific heat = 109.008 grams. 

Platinum, 22.810 " "0.0324 " •' = 0.706 " 

Value in water of the chamber and accessories = 109.714 " 
Thermometer, weight of glass immersed, 12 grams at 0.198 = 2.400 " 
Mercury, 63 " " 0.332 = 2.070 " 

Total equivalent of water = 114. 184 " 

which added to the 2 kilograms of water in the bath makes a 
total of 2 1 14. 184 grams of water. 

The calorimetric weight for the Berthelot bomb at the 
College of France in 1888 was 398.7 grams for bomb and 
accessories. 

The water value of the calorimeter used by Lord and Haas 
at the Ohio State University, Columbus, O., was determined 
as 465 grams. Mahler's apparatus had a water equivalent 
of 481 grams. Still, it is better to determine this equivalent 
by actual experiment, as we are not sure of the specific heat 
of the metal of the bomb, which might, however, be deter- 
mined by a sample taken from the original block of which it 
was made. 

Several methods may be employed for this. 

When we use the calorimetric bomb, we burn in the obus, 
using 2000 grams -of water, a known quantity of a substance 
of fixed composition, and of which the heat of combustion 
is known, as sugar, or naphthalin. We then use less water 
and burn a smaller quantity of the substance. If 1 gram of 
substance was taken the first time, we may take 0.8 gram with 
1800 grams of water the second time. We then have two 



CA L ORIME TRY. 1 5 

equations, rrom which we eliminate the heat of combustion of 
the substance and deduce thence the value in water of the 
cylinder, etc. 

This method, suggested by Berthelot, may be replaced by 
the following, to which he gives the preference: 

Pour into the calorimeter a certain quantity of warm 
water, at 6o° C. for instance. This water is previously con- 
tained in a bottle, and the temperature is measured by a 
thermometer placed inside. As control, operate first without 
the bomb in the cylinder and afterwards with it in place. 

One test of this kind gave Berthelot a value of 354 calories 
for the bomb. The value deduced by calculation from specific 
heat was 355.4. Below is the detailed calculation giving the 
separate parts of the bomb. 





Soft Steel. 


Platinum. 


Brass. 


Names of the Different Parts. 


Weight 

in 
Grams. 


Value in 
Water. 


Weight 

in 
Grams. 


Value in 
Water. 


Weight 

in 
Grams. 


Value in 
Water. 




1709.7 

221.2 

II. 7 


187.61 

24.28 

1.28 


728.8 
528.8 


23.63 
17.15 


20.0 

3-97 

IO8.9 










1.86 


Cone-screw and socket 






0.37 


Movable accessories serv- 
ing for suspension and 






33-0 


I.07 




802.7 


88.08 






IO.13 














2745.3 


301.24 


1290.6 


41.85 


132.9 


12.36 





Recapitulation. 



Metals Used. 



Steel 

Platinum 

Brass (calorimeter and agitator omitted). 



Weight of bomb 

Value in water by direct test. 



Weight in 
Grams. 



2745.3 

1290.6 

132.9 



4168.8 



Calculated 
Value in Water. 



301.24 
41.85 
12.36 



355-45 
354-7 



1 6 CALORIFIC POWER OF FUELS. 



CORRECTIONS FOR THE READINGS. 

The corrections to be applied to thermometric readings, 
besides those due to the thermometer itself, are of various 
kinds, and naturally vary with the kind of calorimeter used. 
Some, however, are common to all. 

The correction relative to heating and cooling concerns all 
calorimeters. Favre and Silbermann made this correction with 
a coefficient previously determined, once for all, by a series 
of experiments. For example, the coefficient that they found 
for their calorimeter (± 0.0020225) represents the influence 
of the external temperature through the envelopes and pack- 
ings for one minute and one degree. 

Instead of a coefficient of correction thus determined, 
use preferably a system of correction devised by Regnault and 
Pfaundler. This system is superior to the preceding, as it 
allows consideration of all external conditions at the time of 
the experiment. It is evident, for example, that the evapora- 
tion of a liquid may vary in such proportions that a fixed 
coefficient will not always represent it. 

The system of Regnault and Pfaundler does not need 
previous experiments nor a determined coefficient. It rests 
on observation of the thermometer immersed in the bath a 
few minutes before and after the experiment, or at the times 
when external influence is at its minimum or maximum. 
Knowing the value of these two kinds of influence, it is 
easy to calculate it for the whole duration of the test. 

It is well to continue the observations before combustion 
for some five minutes. These five minutes should be pre- 
ceded by at least ten minutes' immersion of the combustion 
chamber with agitator, so as to establish equilibrium of tem- 
perature between the cylinder and the water. 

Suppose the initial correction corresponding to the first 
period to be zero — which is rare, it is true, but simplifies the 



CALORIMETRY. 



17 



demonstration — and that the observations have given the fol- 
lowing data: 

Initial temperature of bath 18.460 

After 1 minute 19. 700 



10 



20.540 
20.670 
20.680 
20.676 
20.665 
20.655 
20.640 
20.630 
20.620 



The combustion once commenced is continued till after 
the fourth minute and ends between the fourth and fifth 
minutes, but the equilibrium of temperature between the bath 
and the combustion-chamber is not established until the 
eighth minute, the time when the variation due to difference 
between them has become regular (0.0 io° per minute). 

A table of corrections is formed as follows: 





18.460* 


1st minute. .. . 19.700 


2d 


' 20.540 


3d ' 


1 20.670 


4th ' 


' 20.680 


5 th < 


' 20.676 


6th ' 


20.665 


;th ' 


' .... 20.655 


8th ' 


' 20.640 


9th ' 


' .... 20.630 


oth 


' 20.620 



Mean 19.080' 
20. 120 
20.605 
20.675 
20.678 



Difference 0.620 
1.660 
2.145 
2.215 
2.218 



1 8 CALORIFIC POWER OF FUELS. 

The total elevation of temperature is 

20.676 — 18.460 = 2.2 16 , 

and the correction is 

20.676 — 20.620 = 0.056 for five minutes, 
or 0.011 for one minute. 



Then 



2.216 : 0.011 = 0.620 : 0.0031 
2.216 : o.on = 1.660 : 0.0083 
2.216 : 0.011 = 2.145 : 0.0107 
2.216 : 0.011 = 2.215 : 0.0110 
2.216 : 0.011 = 2.218 : 0.0110 



Total 0.0441 

There is then 0.0441 ° to be added to the difference, 2.2 16 , 
increasing it to 2.260 , which is the corrected difference of the 
bath temperature, from which the heat of combustion of the 
substance burnt in the calorimeter is calculated. 

Regnault and Pfaundler's formula is 

Atn — A to + K{tn— to) ; 

in which 

Atn = ascertained variation of temperature from the heat- 
ing and cooling of the calorimeter for one 
minute; 
Ato = variation at the beginning; 
tn — to = loss or gain during the total time of the test; 
n = number of minutes of test. 

Using the above numbers, 

K = 7 = 0.00496. 

2.216 ^ 



CA L ORIME TRY. 1 9 

It will suffice, then, to find the total loss or gain to take 
the sum of all the gains or losses calculated by means of the 
coefficient K during the whole time of the experiment. 

Thus, 

0.620 X 0.00496 = 0.003 1°, 
1.660 X 0.00496 = 0.0083 , 
and so on. 






CHAPTER IV. 
CALORIMETERS WITH CONSTANT PRESSURE. 

The first calorimeters were of constant pressure; that is, 
the combustion was carried on at the atmospheric pressure or 
very near it, and did not vary from the beginning to the end 
of the experiment. Hence the modifications in the volume 
of the gases before and after combustion exercised no influ- 
ence on the observed results. 

Rumford, in 1814, was the first who tried to correct 
external influences. He employed a practical method which 
has often been used since, and consists in giving the calo- 
rimeter bath a temperature in the beginning of the test less 
than that of the room, and allowing it at the close to attain 
a temperature in the same proportion above that of the room. 
His calorimetric apparatus was composed of a copper boiler 
of several litres capacity, heated by an interior tube through 
which passed the gaseous products of the combustion. The 
combustible was burnt in a little burner placed under the 
boiler, and the air used circulated around the heater before 
passing to the burner, thus preventing any loss of caloric by 
radiation. 

Dulong in 1838 used oxygen, and obtained much superior 
results. His calorimeter consisted of a rectangular copper 
box, 25 centimetres (about 10 inches) deep, 7.5 centimetres 
(2.9 inches) wide, and 10 centimetres (3.9 inches) long. It 
was closed at the upper part by a cover with a mercury seal. 



FAVRE AND SILBERMANN' S CALORIMETER. 21 

The oxygen passed into the calorimeter by a copper tube 
opening at one of the sides of the box near the bottom. 
The gases of combustion were drawn into a gas-holder. The 
apparatus was enclosed in another likewise rectangular, in 
which was put 1 1 litres (9! quarts) of water. This was the 
calorimetric cylinder. The water was kept in motion by an 
agitator. 

The unit chosen by Dulong was one gram of water whose 
temperature was raised one degree. He corrected the tem- 
perature observed, same as Rumford, but he also noticed 
that this correction was correct only when the first period 
was equal to the second. The results obtained by Dulong in 
1838 were not published till after his death, in 1843. For 
hydrogen and carbonic oxide they are but slightly different 
from the most modern determinations. 

CALORIMETER OF FAVRE AND SILBERMANN. 

In 1852 Favre and Silbermann published their first 
researches on the quantities of heat generated by chemical 
action and described their calorimeter. 

All rapid-combustion calorimeters and all with constant 
pressure intended for solid bodies are copied more or less after 
that of Favre and Silbermann. The principle and mode of 
execution in their general lines are the same; the form in some 
details or the material employed for the combustion-chamber 
has been modified more or less; but the general apparatus 
and accessories, as well as the method, have remained as 
F. & S. left them. We will describe, then, this calorimeter 
in its details, and outline the modifications made by other 
experimenters. 

The calorimeter called Favre and Silbermann's is composed 
of three concentric copper cylinders (Fig. 2, B, C, D). 
Cylinder B is the calorimeter cylinder; it is silver-plated and 
polished on the inner surface so as to lessen its emitting 
power; its capacity is a little over 2 litres (3 J- pints), being 20 



22 



CALORIFIC POWER OF FUELS. 



centimetres (about 8 inches) high and 12 centimetres (4J 
inches) in diameter. In the middle is placed the combustion- 
chamber A (Figs. 2 and 3). 





Fig. 2. Fig. 3. 

Favre and Silbermann Calorimeter. 

The combustion-chamber is of burnished gilt copper, and 
is shown in Fig. 3. It is a slightly conical vessel, the large 
opening in which receives a stopper from which is suspended 
the burner made of a material suitable to that of the sub- 
stance operated on. The stopper itself carries two tubes, m 
and n, the first being an observation tube for the combustion, 
and is surmounted by a mirror. M, which allows examination 
during the burning. The mirror receives light by the tube 
m, which is closed by an athermanous system of quartz, 
alum, and glass. The other tube, n, carries the jet for the 
oxygen. Tube b is closed, or removed during the test with 
coal, as it is of no use then. Tube c serves as the exit for the 
waste gases of the combustion, which pass through the coil cc 
(Fig. 2) before reaching the analytical apparatus. This coil 



FAVRE AND SILBERMANN'S CALORIMETER 



23 



is sufficient to cool the gas to the temperature of the bath. 
Experimenters should solder the oxygen-jet to the stopp'er 
so as to diminish the number of openings. It is also advan- 
tageous to solder the coil to the cover. 

Certain fuels with very smoky flames require the addition of 
oxygen very near their surfaces. Scheurer- 
Kestner and Meunier-Dollfus employed the 
following arrangement (Fig. 4), a being the 
platinum capsule; cc\ the platinum tube, 
which at the part c fits tight in the mouth 
of the oxygen-jet; b, b, b, platinum suspen- 
sion-rods; d, fuel. 

It is impossible to prevent the genera- 
tion of more or less hydrocarbons and car- 
bonic oxide. The weight of the hydrogen 
and carbon is determined by causing the 
gaseous products of combustion to pass 
through an organic analysis tube, after re- 
moving the water and carbonic acid. For 
this purpose the exit-tube c (Fig. 3) is con- 
nected by a caoutchouc tube with a Liebig apparatus, fol- 
lowed by a U-tube of soda-lime. 

The gas-current being rather rapid, an absorption appa- 
ratus must be used, large and powerful enough to completely 
free the gas from the carbonic acid and water before it reaches 
the red-hot copper oxide. This is done by passing the gases 
through another U-tube smaller than the preceding, and whose 
weight should vary only a few milligrams. The gases thus 
freed pass to the tube of hot copper oxide, where the com- 
bustible gases are burnt to water and carbonic acid, which are 
collected and weighed as usual. 

Scheurer-Kestner and Meunier-Dollfus employed a plati- 
num combustion-tube, and prefer soda-lime as absorbent for 
the water after the conclusive experiments by Mulder.* 
*Zeitschrift fur analytische Chemie, I. 4. 




24 CALORIFIC POWER OF FUELS. 

The coal for the experiment must be in pieces; if in 
powder, the combustion is more difficult, unburnt gases 
escaping in considerable quantities, so that it is rare to obtain 
a complete combustion, and the cinders almost invariably 
contain small quantities of coke. To determine these, the 
capsule and tube are withdrawn from the combustion-cham- 
ber, dried, and weighed. The coke and the little soot on the 
sides of the capsule are burnt off by calcination in the air and 
a new weighing made, giving the weight of the carbon and 
cinder — elements which must be considered in the corrections. 
From half a gram to a gram of coal may be used. 

When the combustion-chamber containing the weighed 
substance is put into the calorimeter all the parts of the 
apparatus are connected by caoutchouc joints and tested. 
A slow current of oxygen * from a gas-holder is passed 
through the apparatus. The combustible is ignited by a few 
milligrams of burning charcoal, the joint [ in the tube being 
broken for the moment, and immediately reconnected without 
stopping the flow of oxygen. The little glass M allows inspec- 
tion of the combustion, the intensity of which can be regulated 
by the flow of oxygen from the gas-holder. The temperature 
shown by the thermometer is recorded each minute to obtain 
the data necessary for the correction spoken of above (pages 
1 6 et seq,). 

To calculate the heat-units developed by the combustion 
the following elements are needed : 

i. Weight of the combustible used; 

2. Weight of the carbon remaining in the cinders unburnt 
or as black; 

3. Weight of the cinders; 

4. Weight of hydrogen escaped unburnt; 

* To prepare the oxygen a copper flask of one litre capacity is used, in 
which is placed some chlorate of potash, which is then heated by a gas 
flame. The gaseous current is very regular, except towards the end, when 
it may become tumultuous. The addition of a small percentage of black 
oxide of manganese promotes the regularity of the gas generation. 



FAVRE AND SILBERMANN'S CALORIMETER. 2$ 

5. Weight of carbon escaped unburnt in the gaseous 
products; 

6. Elevation of temperature of calorimeter bath; 

7. Correction for heating and cooling caused by external 
influences on the calorimeter cylinder. 

The combustion of the coal by this means is rarely com- 
plete; there remain variable quantities of coke mixed with 
the cinders formed. An uncertainty attends the calorimetric 
value according as the combustion was slow or rapid, since 
this small quantity of coke contains more or less hydrocarbons. 
These differences, however, apply within very close limits, so 
that no fear need be entertained of large errors therefrom. 
When a coal, in pieces, has been burnt, there remains in the 
capsule only a few milligrams of coke or unburnt carbon. 
From this we calculate the calorimetric value, using 8080 as 
coefficient (heat of combustion of charcoal according to Favre 
and Silbermann); and in using that coefficient the hydrogen 
which may exist in the coke is naturally neglected, but this 
cannot be prevented. The carbon and hydrogen of the com- 
bustible gases which escaped combustion are transformed into 
water and carbonic acid, and weighed as such. The hydrogen 
is calculated as in the free state (coefficient 34500) and the 
carbon as carbonic oxide (coefficient 2435). 

It is evident that these are only approximations, since the 
hydrogen is not disengaged in a free state, but as a hydro- 
carbon; and its coefficient (34500) should be diminished by the 
heat of formation of this compound, or, in other words, by the 
heat of combustion of hydrogen and carbon. This correction, 
however, is not possible; for neither the composition nor state 
of molecular condensation of such hydrocarbon is known. 
Similarly for the carbon, and its heat of combination in the 
carbon compound. There are, then, some uncertainties, 
but not of much importance, in the determination of the heat 
of combustion of fuels — uncertainties which the use of the 
calorimetric bomb has entirely avoided. 



26 CALORIFIC POWER OF FUELS. 

A complete test will now be described, giving all the cor- 
rections. 

Suppose one gram of dried coal in fragments is used. 
After combustion in the calorimeter, weigh the capsule con- 
taining the cinders. 

Cinders after combustion o. 1 10 gram. 

" " calcination in the air o. ioo " 

Unburnt carbon remaining in cinders.... o.oio " 

Then 

Coal used, dried at ioo° C 1.000 gram. 

Cinders o. i oo ' ' 

Pure coal (cinders out) 0.900 " 

Carbon not burnt during the experiment.. 0.010 " 

There was collected from the combustion of the hydro- 
carbons and the carbonic oxide o. 10 gram of carbonic acid, 
corresponding to 0.006 of carbonic oxide (molecular ratio 
11 :/); also 0.0 10 gram of water, corresponding to 0.0011 
gram hydrogen (molecular ratio 9 : 1). 

Increase of temperature of the bath 3.702* 

Correction 0.020 

Total increase 3.722* 

Calorimeter equiv. in water 2. 114 kilos * and 3.722 X 2. 114 =7.8683 

Unburnt carbon 0.010 X 8.080 cal. = 0.0808 

Carbonic oxide 0.006 X 2.403 " =0.0144 

Hydrogen o.oon X 34.500 " = 0.0383 

Total calories from 0.900 gram coal completely burnt = 8.0018 

1 gram pure coal = 8.891 calories, 

1 kilogram pure coal = 8891 calories, or 
1 pound " " = 16003.8 B. T. U. 

* 2000 grams of water + 114 grams for value in water of calorimeter and 
accessories. 



FAVRE AND SILBERMANN' S CALORIMETER. 



27 



In this example the corrections are not very important, 
since they do not exceed one-half per cent. These are the 
ordinary conditions when the coal used is in pieces. With 
pulverized coal, on the contrary, the quantity of unburnt 
carbon and of combustible gases increases considerably and 
renders results less certain. The oppor- 
tunity we have to weigh the cinders of 
each test obviates pulverization of the coal 
to obtain an average sample of the cinders. 

Favre and Silbermann's calorimeter has 
been modified by Berthelot in several par- 
ticulars.* He has happily modified the 
agitator and given it a coiled form, as 
shown in Fig. 5, a detailed description of 
which is given in his Essai de Me'canique 
Chimique, p. 145. 

This agitator has the advantage over 
the old one of more completely mixing 
the water, with less force, and without 
accelerating evaporation. Fig. 5 shows 
it placed in the middle of the calorimeter. 
He has also replaced the gold-plated copper combustion- 
chamber by the glass apparatus which Alexejew used for 
combustibles. 




Fig. 5. 



*The F. & S. calorimeter with all accessories and an agitator (not me- 
chanical) costs about 500 francs ($100.00); with mechanical agitator arranged 
for a laboratory turbine or dynamo the cost is about 600 francs ($120.00). 
Berthelot's calorimetric bomb of platinum, enamelled inside and not 
double, costs no more, and is much preferable. A single operator can 
handle it, while the F. & S. apparatus requires two. 

Nevertheless, the manner of working the F. & S. calorimeter is de- 
scribed in detail, because its use is surrounded by conditions easily realized 
in all countries. The calorimetric bomb requires oxygen compressed to 25 
atmospheres, which cannot be obtained everywhere. 



28 



CALORIFIC POWER OF FUELS. 



ALEXEJEW'S CALORIMETER. 

The apparatus used by Alexejew was composed of a glass 
combustion-chamber A (Fig. 6), in which he burnt the coal 

previously reduced to fragments. 
These fragments were placed on a 
platinum grating in the centre of 
the chamber. The fuel was kindled 
by means of a platinum sponge 
placed over it, on which impinged 
a jet of hydrogen from the gas- 
holder M, opening at c, correction 
for which is of course made in the 
calculation. The grating contain- 
ing the fuel was suspended from 
the glass rod a. As soon as the 
combustion was started the current 
of hydrogen was cut off by the cock 
/, and the oxygen allowed to flow 
in through b, the waste gases pass- 
ing out through the coil. If the 
combustion was interrupted, it was 
rekindled by the hydrogen and 
platinum sponge. The hydrogen used was calculated in grams 
and multiplied by 34500. The number of calories thus ob- 
tained was deducted from that calculated from the rise in 
temperature of the bath. According to Alexejew, the im- 
portance of this correction never exceeded one-half per cent, 
and he never had to rekindle the fuel. 

Alexejew did not determine the unburnt gases, as experi- 
ence showed they never exceeded 0.35 per cent. It is im- 
possible, however, to determine the hydrogen of the hydro- 
carbons if desired, as these would be mixed with the hydrogen 
used for kindling, part of which may escape combustion. 
The kindling with hydrogen might, however, be replaced by 
that with carbon, as in the F. & S. apparatus. 




Fig. 6. — Alexejew Calorim- 
eter. 



FISCHER 'S CAL ORIME TER. 



2 9 



Burning the fuel on a grating renders it impossible to 
weigh the cinders, and this inconvenience is of more impor- 
tance as the coal is used in pieces. The use of pastilles is not 
possible, as they splinter in burning. 

The calorimeter contained 2500 grams '(5.5 11 lbs.) of 
water, a quantity somewhat larger than that usually employed, 
and which is based on the sensibility of the thermometer. 
To attain the same degree of precision it was necessary to use 
larger samples of fuel or else have more delicate thermometers. 
The water was kept in motion by the coil-agitator. 



FISCHER'S CALORIMETER. 

Fischer made a combustion-chamber of silver 0.940 fine, 
so that it would be less easily attacked 
by sulphur, from which the gaseous pro- 
ducts of coal are rarely free. He drew 
off the waste gases at the bottom of the 
apparatus (Fig. 7), thus avoiding the in- 
convenience of exit-tubes in the cover 
of the combustion-chamber. The cool- 
ling coil was replaced by a flattened 
pipe of a certain size. A represents 
the combustion-chamber. The oxygen, 
purified by passing over potash and 
then dried, arrived by the tube a fast- 
ened in the tube of the cover by a 
caoutchouc joint, and passed by means 
of the platinum tube r into a crucible 
z of the same metal, containing one 
gram of the fuel. The crucible was 
covered by a grating, which became 
red-hot towards the end of the opera- 
tion. This was intended to burn the 
waste gases, and the black deposited at the beginning. The 
gases flowed out at t, and after having encircled the outside 




Fig. 7.— Fischer's Cal- 
orimeter. 



30 



CALORIFIC POWER OF FUELS. 



of the crucible escaped at b. The thermometer t showed 
whether the temperature of the gases was the same as that 
of the bath. 

The calorimetric bath contained 1500 grams (3.3 lbs.) of 
water, and was protected against external influences by a 
wood casing, while the space C was filled with glass wool ; 
but this is not necessary, n is a brass cover which may be 
dispensed with. The thermometer T is the calorimetric 
thermometer; m is an agitator moved by the string 0. The 
value in water of the one used by Fischer was 1 1 3. 5 calories. 
The coal was dried in nitrogen. The carbonic acid and the 
unburnt carbon were determined. 

thomsen's calorimeter. 



This calorimeter was designed especially for tests of gases 
and vapors. It is not adapted to tests of solid fuels. It 

consisted (Fig. 8) of a calorimetric 
bath of thin brass, with a capacity 
of some 3 litres (195 cubic inches), 
protected from radiation by a cylin- 
drical ebonite envelope ; and a plati- 
num balloon of half a litre (32.5 
cubic inches) capacity, in which the 
gases were burnt, being delivered 
through the opening at the bottom. 
The waste gases passed off 
through a coil, and a mechanical 
agitator kept the water in circula- 
tion. 

The dried gas was delivered 
with perfect regularity from a mercury gas-holder, sufficient 
air or oxygen being added to render it free-burning, and 
enough oxygen was supplied to insure perfect combustion. 
This he attained by always having 40 to 50 per cent in the 




-Thomsen Calo- 
rimeter. 






CARPENTER'S CALORIMETER. 3 1 

waste gases. The gases passed off through a carbonic acid 
absorbing apparatus. 

To reduce to the minimum, or entirely suppress, the cor- 
rection for temperature he regulated his gas-flow so that the 
temperature was as much higher than the air at the close of 
the experiment as it was lower at the beginning. This he 
easily did by means of his hydrogen supply. If a liquid was 
tested, it was vaporized and burnt in a specially devised 
burner which allowed complete combustion of almost all com- 
pounds not having too high a boiling-point. If too high for 
heat vaporization, they were carried along by a current of air, 
oxygen, or hydrogen, as seemed best adapted. 

The water of the calorimeter being weighed, the lower 
portion was closed with a rubber stopper and by means of an 
aspirator a pressure of 8 to 12 inches of water was put on the 
apparatus to test the joints. When ready, the temperature 
of the bath and the air was noted for some minutes, the gas- 
holder reading taken, the burner placed in position, and the 
test commenced. The depression produced by the aspirator 
was about 0.4 inch during the whole test. The regularity of 
the working was shown by a gauge registering the pressure. 
When the temperature had reached the desired point the gas 
and electric current were shut off, the burner removed, and 
the opening closed again. The aspirator was used to draw 
dry air, freed from CO, , through the apparatus to insure 
removal of all waste gases. The apparatus was then allowed 
to rest, taking the temperature at short intervals for fifteen 
minutes. He then had all the data required. 

carpenter's calorimeter. 

Prof. R. C. Carpenter devised a calorimeter especially for 
coal determinations, which is a modification or extension of 
Thomsen's. He has used it considerably in connection with 
work he has been engaged on, and the results credited to him 
in the tables at the end of the book were obtained with it. 



32 



CALORIFIC POWER OF FUELS. 



Fig. 9 is a sectional view of his apparatus. It consists of 
a combustion-cylinder, 15, with a removable bottom, \J, 




Fig. 9. — Carpenter Calorimeter. 

through which passes the tube, 23, to supply oxygen, and also 
the wires, 26 and 27, to furnish electricity for the igniter. 
It also supports the asbestos combustion-dishes, 22, used for 



CARPENTER'S CALORIMETER. 33 

holding the fuel. At its top is a silver mirror, 38, to deflect 
the heat. The plug is made of alternate layers of asbestos 
and vulcanite. The products of combustion pass off through 
the spiral tube, 28, 29, 30, 31, which is connected with the 
small chamber, 39, attached to the outer case of the instru- 
ment. This chamber has a pressure-gauge, 40, and a small 
pinhole outlet, 41. Outside the chamber is the calorimetric 
bath, 1, which is connected with an open glass gauge, 9, 10. 
Above the water is a diaphragm, 12, used to adjust the level. 

The calorimeter h'as an outer nickel-plated case, polished 
on the inside. The bath holds about 5 pounds of water, and 
uses about 2 grams of coal at a time. It is thus considerably 
larger than the bomb, and the charge being larger the time 
consumed by the test is longer, being some ten minutes for 
each gram burnt. The entire outside dimensions of the case 
are 9^ inches high and 6 inches diameter. 

In using the apparatus the coal is ground to a powder in a 
mill or mortar. The asbestos cup is heated to burn off all 
organic matter and weighed. The sample is then placed in 
it, and the whole weighed again. This gives the weight of 
the coal used. Place it in the combustion-chamber, raise the 
platinum igniting wire above the coal, make the connections 
with the battery, and as soon as the heat generated causes the 
water to rise in the glass tube turn on the oxygen, and by 
pulling down the wires kindle the coal. At this instant the 
reading on the glass scale must be taken. 

By means of the glasses 33, 34, and 36 watch the 
progress of the combustion, and as soon as finished take the 
scale-reading and the time. The difference between this 
scale-reading and the one previously made is the " actual " 
scale-reading. 

To correct for radiation, allow the apparatus to stand with 
the oxygen shut off for a length of time equal to that of the 
combustion, and take the scale-reading and the time. The 



34 CALORIFIC POWER OF FUELS. 

difference between this and the " actual " reading is to be 
added to the " actual " for the " corrected " reading. 

Now, by inspection of the calibration-curve previously 
prepared, at the point corresponding to the corrected scale- 
reading will be found the B. T. U.'s for the quantity burnt. 
The ash is determined by weighing the asbestos cup after the 
combustion. 

The following shows all the calculation needed: 

Weight of crucible (asbestos cup) .... 1.269 grams. 

" " " and coal 3 .017 " 

" ash 1.567 " 

" "■ combustibles I-450 " 

" " ash 0.297 " 

" " coal 1-747 " 

1.747 grams X 0.002205 = 0.003852 pounds. 

First scale-reading 3.90 inches; time 2 hrs. 55 m. 

Second" " 1470 " " 3 " 20" 

Third " " 14.30 " " 3 " 45 " 

"Actual" scale-reading. 14.70— 3.90= 10.80 inches. 
Radiation correction 14.70— 14.30= .40 " 



Corrected reading 11.20 " 

On the calibration-sheet II. 2 corresponds to 46.25 
B. T. U.'s, and 46.25 B. T. U. -=- 0.003852 = 12000 B. T. U. 
per pound. 

All air must be removed from the water in the bath, 
the apparatus must work at a constant pressure, and the 
pressure for which it is calibrated. A pressure of 10 inches 
of water has been found satisfactory. Complete combustion 
is always attained in the asbestos cups. 

It will be seen that the use of thermometers is obviated, 
and also all corrections but one. The apparatus is intended 



SCHWA CKHOFER 'S CAL ORIME TER. 



35 



for ordinary every-day work, and will give good comparative 
results when used according to directions, which must be 
implicitly followed. The amount of calculation is reduced to 
a minimum, and there are no delicate parts requiring extra 
care and adjustment. For the purpose intended, it seems an 
advance over the others previously used, which could never 
give more faint approximations to correct results. 

schwackhofer' s calorimeter. 

In 1884 Schwackhofer published calorimetric researches 
on different kinds of coal, using a calorimeter in which he made 




Fig. 10. — Schwackhofer Calorimeter. 



several modifications intended to render it specially applicable 
to such fuel. 

He considered it advisable to use as much as five or six 
grams of coal, which is six times that generally used. He 
burnt at the same time and under definite conditions, shown 



3^ CALORIFIC POWER OF FUELS. 

in the sketch (Fig. 10), a certain quantity of sugar-charcoal, 
the combustion of which was intended to accelerate and com- 
plete that of the coal tested. 

In the figure (Fig. id) ab represents the combustion-cham- 
ber, c the calorimetric bath. Minor details of accessories, en- 
velopes, regulators, etc., are omitted. The burner proper is of 
platinum and of two pieces, a and b, superimposed, the coal 
being placed in the lower portion, the sugar-charcoal in the 
upper one. All pieces of the burner may be removed for the 
introduction of the coal and for cleaning. The two combus- 
tibles rest on perforated plates of platinum, in which the per- 
forations, made by a special machine, are so small that light 
can hardly pass through, and from which the cinders can be 
completely removed ; the holes in the upper one are slightly 
larger than those of the lower. The oxygen enters through 
three tubes, e, f, g. Tubes g and m pass outside the bath, and 
carry mirrors to allow inspection during the burning. The 
waste gases pass off at the bottom through a coil n } and are 
collected in H. This vessel is simply to detect smoking, he 
having found that it happened only when the pressure was di- 
minished at the burner, and that it could be stopped by a rein- 
statement of the normal pressure, p represents an aspirator, in 
which are collected the waste gases. Another one, not shown 
in the sketch, serves to contain the gas analyzed. Both are 
filled with water covered with a film of oil. The oxygen 
passes through a jar s filled with soda-lime, a bottle o fur- 
nished with a thermometer, a cock / as regulator of the flow, 
and one or more wash-bottles q containing sulphuric acid. 

The calorimeter-chamber c contains 5200 cc. (4.6 qts.) of 
water. 5 or 6 grams (jj to 92.5 grains) of coal were used, with 
2 to 4 grams (31 to 62 grains) of sugar-carbon of a known 
calorific value. The temperature of the bath rose about 10° 
C, and the experiment generally lasted an hour. 

The sugar-carbon was first kindled in the upper part of the 
burner, the under portion burning first. From this sparks 



W. THOMPSON'S CALORIMETER. 2)7 

were thrown to the coal, and it soon kindled. The oxygen 
flowed in by g and e. When combustion was well under way 
and had reached the lower portions of the coal, g was shut off 
and /opened. 

Schwackhofer obtained complete combustion of the sugar- 
carbon and coal, with no formation of black, and no residue of 
coke. 

The gaseous product of the combustion was generally of 
the following composition : 

Carbonic acid 50 to 60 percent; 

Carbonic oxide , 1.2 to 0.3 " " 

Oxygen 10 to 15 " " 

Nitrogen 30 to 40 " " 

arising principally from the fact that to keep up the normal 
pressure the combustion-chamber was in communication with 
the open air. The cinders were weighed after each test. 

This apparatus should give exact results, but its use is 
complicated. The long duration of the test requires impor- 
tant corrections for influence of external heat, and it needs 
several thermometers. 

W. THOMPSON'S CALORIMETER. 

W. Thompson devised a calorimeter in which the com- 
bustion is started by a jet of oxygen, but the waste gases in- 
stead of passing through a coil bubble up through the water 
of the calorimetric bath. In this apparatus the uncombined 
gases are naturally neglected. (See Fig. 11.) It is an appa- 
ratus, as the inventor says, not intended for scientific re- 
searches, but for handy use of mechanics or " for popular use." 

a is a galvanized-iron gas-holder containing oxygen ; b, a 
stop-cock regulating the flow of water to this holder; d, stop- 
cock for gas ; e, rubber tube ; f, level-gauge ; g, pressure- 
gauge; k, bell-glass covering the platinum crucible k, in which 
the coal is burnt ; / is a support of earthenware suspended 



33 






CALORIFIC POWER OF FUELS. 



from the bell-glass by metal springs, and intended to insulate 
the crucible and prevent too quick cooling ; tn is a glass jar 
containing 2000 grams (4.4 lbs.) of water, forming the calori- 
metric bath. "Water cannot enter the bell h while the cock j 




Fig. 11. — W. Thompson Calorimeter. 

is closed, and it is opened only when the pressure in the 
gas-holder is sufficient; h is a glass jar filled with water and 
surrounding the calorimetric jar, and / is the agitator. 

One gram of fuel is put into the crucible, and on this is 
placed a small cotton wick impregnated with bichromate of 
potash. This is lighted at the instant of putting into the jar, 
and its combustion aided by the oxygen kindles the fuel. 

This is an imperfect apparatus, and will give in most cases 
only unsatisfactory results. Still it is in rather common use 
in the shops of England, where it serves principally as a com- 
parative measure, the errors being considered constant. 



BARRUS S CALORIMETER. 

The Barrus calorimeter is a modification of the one just 
mentioned. While it requires considerable care in using to 
get correct results, yet it is one of the simplest and most in- 
expensive. 



BARRUS' S CALORIMETER. 



39 



As described by Mr. Barrus, "it consists of a glass beaker 
(Fig. 12) 5 inches in diameter and 1 1 inches high, which 
can be obtained of most dealers in 
chemical apparatus. The combus- 
tion-chamber is of special form, and 
consists of a glass bell having a 
notched rib around the lower edge 
and a head just above the top, with 
a tube projecting a considerable dis- 
tance above the upper end. The 
bell is 2\ inches inside diameter, 5J 
inches high, and the tube above is f 
inch inside diameter and extends 
beyond the bell a distance of 9 
inches. The base consists of a cir- 
cular plate of brass 4 inches in diam- 
eter, with three clips fastened on 
the upper side for holding down 
the combustion-chamber. The base 
is perforated, and the under side 
has three pieces of cork attached, 
which serve as feet. To the centre 
of the upper side of the plate is attached a cup for holding 
the platinum crucible in which the coal is burned. To the 
upper end of the bell, beneath the head, a hood is attached 
made of wire gauze, which serves to intercept the rising 
bubbles of gas and retard their escape from the water. The 
top of the tube is fitted with a cork, and through this is 
inserted a small glass tube which carries the oxygen to the 
lower part of the combustion-chamber. This tube is movable 
up and down, and to some extent sideways, so as to direct 
the current of oxygen to any part of the crucible and to 
adjust it to a proper distance from the burning coal." 

The method of working it can be easily seen from the 
description and cut. In burning very smoky coals he mixes 




Fig. 



12. — Barrus Calorim- 
eter. 



40 



CALORIFIC POWER OF FUELS. 



them with a proportion of non-smoking coal of known calo- 
rific value, and when anthracite or coke is burnt he mixes it 
with a small portion of bituminous coal. In Mr. Barrus's 
hands very satisfactory results have been obtained. 



HARTLEY AND JUNKER' S CALORIMETER. 

Hartley's calorimeter is an apparatus of constant pressure 
and continued combustion. The gas measured by a meter is 
burnt in a Bunsen burner surrounded by a cylindrical copper 

si 




Fig. 13. — Junker Calorimeter. 

vessel filled with water, which is constantly renewed. The 
flow of liquid is such as to avoid much heating and time suf- 
ficient is used to increase the temperature so as to have a good 
thermometric observation. The volume or weight of the water 
is determined at such intervals and the thermometric readings 
taken often enough to obtain an average. 



JUNKER'S CALORIMETER 4 1 

Hugo Junker's modification of the apparatus rendered it 
more exact. It has been used for some time in Germany 
and in the United States. It is composed (Fig. 13) of a 
gas-meter #, preceded by a very sensitive regulator b. On 
leaving the meter the gas passes to a Bunsen burner c. The 
products of combustion give up their heat to a calorimetric 
tube d, through which regularly flows a stream of water. The 
temperature of the gases is regulated by means of a thermom- 
eter e. In order to keep the flow of water as regular as pos- 
sible, it flows from the supply-tube g into a small reservoir 
kept at a constant level governed by the tube h. The water 
passes through i to the calorimeter and escapes at k, run- 
ning into the glass in which it is measured or weighed. The 
graduated tube / is to catch the condensed water from the 
interior of the calorimeter. The thermometer m shows the 
heat of the escaping water, and n that of the water enter- 
ing the calorimeter. 

To calculate the calories generated during the combustion 
proceed as follows: 

Measure the quantity of water which runs through it in 
one minute, take the temperature of the two thermometers, 
and note the flow of gas. The heat of combustion per cubic 
metre of burnt gas is obtained by multiplying the volume of 
water flowing per minute by the difference of the two temper- 
atures and dividing the product by the gas volume burnt per 
minute. 

Thus : 

Volume of water flowing per minute.... 902.3 cc. 

" " gas burnt per minute. .... . 2500.0 cc. 

Temperature at inlet 13. i° C. 

" outlet 27. 5 C. 



1 1 



902.3 X (27.5 - 13. 1) . 

Q = = Uqo calories. 

2.5 



42 CALORIFIC POWER OF FUELS. 

The gas tested has a value of 5 196 calories per cubic metre. 

Since the calorie is 3.968 times the B. T. U., and the 

cubic metre is 35.316 times the cubic foot, multiplying- 

1 • , • , 3.968 

the calories per cubic metre by — = 0.1121; will eive 

35.316 " * 

B. T. U.'s per cubic foot. 
Multiplying, then, 

5196 X 0.1 1235 = 583.8 B. T. U.'s per cubic foot. 

The above example considered the volume of the water. 
It is sometimes advisable to consider the weight instead. The 
following example illustrates this: 

Weight of water used during the test 2000 grams. 

Volume of gas burnt 7- 2 3 litres. 

Temperature at inlet 14-4° C. 

" outlet 36. 5 C. 

Then 

2000 X ( 36.5 - H -4) . . . .. . . 

Q = = 6102 calories per cubic metre. 

7.23 F 

and 

6102 X 0.1 1235 = 685.6 B. T. U. per cubic foot. 

Two causes of error may occur. It is not certain that the 
combustion of the gas in the burner is regular; indications by- 
gas-meters are not always very sure, the start being capricious. 
But these do not have much weight in its use for industrial 
purposes, for which it is chiefly designed. The results are 
very near those obtained by other methods. Stohmann, whose 
competence in such matters is universally recognized, says 
they give good results. 

Bueb-Dessau, to prove the calorimeter, burnt hydrogen 
prepared by electrical decomposition, and obtained after cor- 
rections for thermometer and barometer 34150 calories per 



LEWIS THOMPSON'S CALORIMETER. 



43 






kilogram — a difference of 350 calories from the usual number, 
34500, or only 9 thousandths. 

Prof. Jacobus has determined that there is a constant error 
due to neglect of latent heat of moisture in products of com- 
bustion of —2 per cent in the determinations with this appa- 
ratus; otherwise it is very satisfactory. 



LEWIS THOMPSON S CALORIMETER. 

Lewis Thompson's calorimeter has been used in England 
for some time. It gives only approximate results, but as the 
errors are of the same kind in each case, the results are com- 
parable, and it has been found serviceable in industrial works 
where quick and comparative observations are required. 

The apparatus (Fig. 14) is composed of a glass calorimeter- 
bath H containing water, a copper cylinder E in which the 








Fig. 14. — L. Thompson Calorimeter. 



Fig. 15. — Calorimeter 
in Action. 



mixture of coal and potassa chlorate is placed, and surmounted 
by the nitrate of lead fuse F. Enclosing this cylinder is a bell 
D, having a tube C carrying a stop-cock. The cock is closed 
before putting it in position in the water. K is a cleaner for 
the tube C, and J is a thermometer. 



44 CALORIFIC POWER OF FUELS. 

The fuze is lighted, and the whole quickly put in the jar of 
water. The mixture of combustible and potassium chlorate 
soon ignites and burns, all the gases generated being forced 
out at the bottom of the bell through the perforations, and 
bubble up through the liquid. After the combustion is finished 
the temperature is taken and the heat-units calculated. 

From 8 to 10 parts of oxidizing mixture is recommended 
for one of coal ; but if the coal is very rich this must be 
increased to 1 1 parts, calculated on the crude coal. With 
pure coal, cinders out, the extreme limits are n and 14 parts. 
It would probably increase the accuracy of the method, if 
the same quantity of oxidizing mixture was employed, what- 
ever the kind of coal used, and to mix with it inert substances, 
as silica or ground porcelain, in quantity varying with the 
richness of the coal. 

Scheurer-Kestner tested this apparatus very carefully, 
using a great variety of fuels whose heats had been previously 
ascertained by means of Favre and Silbermann's calorimeter. 
He found some 15 per cent deficit in the figures, and after 
correcting by this amount the results varied only a few per 
cent from those actually obtained. In thirty different kinds 
of coal tested the average was 1.8 per cent too low. 

The use of this calorimeter requires some skill. Its imper- 
fect insulation requires prompt reading and rapid combustion. 
Care must be taken to work at temperatures very close to 
that of the room, as the calorimetric bath is not protected. 
The proportions of the mixture used vary, not only with each 
kind of coal, but for each sample, on account of the propor- 
tions of cinders. Fat coals require more oxidizer than lean 
coals, as it is evident an increase in quantity of cinders should 
require a decrease in oxidizer. But in changing the propor- 
tions of oxidizer a certain difference in elevation of tempera- 
ture is necessarily produced by the heat of solution of the 
salts left after the combustion. These various causes render 
its working rather delicate, and always uncertain. 



CHAPTER V. 
CALORIMETERS WITH CONSTANT VOLUME. 

The results obtained with a calorimeter of constant volume 
are not exactly the same as those obtained with one of con- 
stant pressure ; but for solid or liquid substances the difference 
is too small to consider, since the volume, as well as that of 
the water produced, is inconsiderable in relation to the volume 
of gas employed. As regards the correction for contraction 
and expansion of the gases, they also are inconsiderable. 

In his Traite de Mecanique Berthelot has shown that 
the heat generated by a reaction between gases at constant 
pressure is equal to the heat of combination at constant 
volume at any temperature whatever, increased by the pre- 
ceding product counting from absolute zero ; and he gives the 
following formula for passing from one system to the other : 

QT P = QT V + o. 5424(^V- N') + o.oo2{N - N')t, 

QTp being the heat generated by the reaction at constant 
pressure, and at the temperature T counting from ordinary 
zero; QT V} the heat generated by the reaction at same tem- 
perature and constant volume ; N, the number of units of 
molecular volume occupied by the components, these being 
taken according to usage equal to 22.32 litres under normal 
pressure at 0° ; N', the corresponding number of units of 
molecular volume occupied by the product of the reaction. 

As example, take the combustion of carbonic oxide at 15 . 
Then we have 

CO + O = CO 3 generates at constant volume 68 calories.* 

* These numbers refer to molecular weights. 

45 



46 CALORIFIC POWER OF FUELS. 

To pass from this to the heat given off under constant 
pressure, observe that CO occupies a unit of volume and O a 
half unit. Then 

N = ij. 

CO, occupies a unit of volume and 

1ST = i. 
Hence N - N' = £., 

At 0° there would be, then, for the difference between the 
heat of combustion at constant pressure and that at constant 
volume, 

-j- 0.542 X i = + 0.271 calories. 

At + 1 5° add to this -\- 0.015, which increases the cor- 
rection then to 0.286. The heat of combustion of carbonic 
oxide at constant pressure and 15 is then -|- 68.29 calories. 

With a solid or liquid, this volume in relation to those 
of the gases formed may be practically neglected, the same 
as with the water; all reduce Ihen to the contraction and 
expansion of the gases. Thus, for naphthalin, this correc- 
tion does not exceed 8.8 in 9692 calories — less than o. 1 per 
cent. 

In case of solids «or liquids with unknown molecular 
weight, as with fuels generally, this difference may still be 
approximately calculated, as it is sufficient to know the volume 
of oxygen used in the combustion and that of the gases pro- 
duced. 

The first calorimeter of constant volume in date is that of 
Thomas Andrews, who in 1848 published results obtained 
with a closed calorimeter. The calorimeter was not applicable 
to solids or liquids ; the combustion of the gases was con- 
ducted as in a eudiometer, but he did not take all the 
precautions necessary to be certain of complete combustion. 



ANDREWS' CALORIMETER. 47 

Nevertheless, the results obtained for certain gases are 
remarkable, considering the elementary character of his 
apparatus and working. The combustion of solids, on the 
contrary, gave worthless results. 

The calorimetric bomb of Berthelot and Vielle seems able 
to replace advantageously all the other calorimeters as much 
by its convenience as by its certainty of results. 

Aime Witz made certain changes in the bomb designed to 
facilitate its use, and devised his "calorimetric eudiometer/' 
in which only gases can be burnt. The apparatus is more 
convenient than the bomb, but this convenience has been 
gained at a sacrifice of precision. It is more an instrument 
for practical use than a scientific calorimeter, but may be 
useful within narrow limits. 

ANDREWS' CALORIMETER. 

In 1848 Andrews published his labors on the heat of 
combustion of bodies, and notably on that disengaged b^ 
combustion of different gases. He used a cal- 
orimeter of constant volume, in which the com- 
bustion-chamber was a copper cylinder (Fig. 
16) weighing 170 grams (6 ounces), of 380 
cubic centimetres (about 23J cubic inches) ca- 
pacity, and capable of resisting the pressure 

exerted by the combustion of the same vol- Fig. 16. 

r 1 c / PUN .., Andrews' Calo- 

ume of olenant gas (C a H 4 ) with oxygen. rimeter. 

At the upper part, the cylinder had a small conical tube 
closed by means of a perfect-fitting stopper b. A silver wire 
a was fixed in this stopper, and to this was soldered a very 
fine platinum wire for igniting the gases by a galvanic 
current. The mixture of gases was prepared as for eudio- 
metric analysis. 

The combustion-chamber was entirely submerged in a 
glass cylinder filled with water, of which the temperature is 




4$ CALORIFIC POWER OF FUELS. 

regulated so as to compensate approximately for the probable 
use, and thus avoid corrections for influence of external air. 
This cylinder was put into another, also of glass. A rotary 
motion imparted to the cylinder aided circulation in the 
liquid during combustion, which usually lasted thirty-five 
seconds. 

Andrews also applied his calorimeter to combustion of 
solids, but judging from the low results he did not have per- 
fect combustion. The results obtained with some of the 
gases, on the contrary, are quite reliable, notwithstanding the 
imperfections of the apparatus. 

CALORIMETRIC BOMB OF BERTHELOT AND VIELLE. 

Of all the calorimeters known to-day, the calorimetric 
bomb of Berthelot is that which offers the most advantages, 
as much from its ease of operation as from the precision of 
its results. Only one operator is needed ; the combustion is 
perfect ; the gaseous products need not be analyzed to deter- 
mine the combustible substance ; no weight save that of the 
substance used is needed ; and it is as applicable to solids and 
liquids as to gases. 

True, its use requires oxygen under high pressure ; but 
this pressure (25 atmospheres) may be readily obtained with a 
compression-pump, which is easily procured; and at the 
present time oxygen may be bought sufficiently compressed 
for the purpose. Berthelot states that as much as 5 or even 
10 per cent of nitrogen is allowable, but that the latter limit 
must not be exceeded. 

Mahler used compressed oxygen, and obtained good 
results with that bought in the Paris market. This gas is 
furnished in steel tubes and under 120 atmospheres pressure. 
The cylinders contain sufficient gas to make a large number 
of experiments before the pressure falls too low, i.e., below 
25 atmospheres. 



BER THEL OT'S CAL ORIME TER. 



49 



Fig. iy shows the bomb adjusted ready to place in the 
calorimeter. Full details of the construction 
will be found in Berthelot and Vielle's treatise, 
Sur la force des metiers explosives, vol. I, p. 
245. 

Fig. 21 shows the arrangement adopted 
by Berthelot to burn solids. The cylinder 
(Fig. 18) is lined with platinum, and con- 
structed so as to resist a pressure of 200 to 
300 atmospheres. It is furnished with a 
tight-fitting head (Fig. 17) fastened ex- 
teriorly by a piece of steel (Fig. 19), clamped 
on the external face of the bomb by a screw- 
clamp (Fig. 20), which does not form a part of the apparatus 
as immersed. 

The sealing of the bomb results from the adherence of 
the margin of the head BB (Fig. 21), and the interior of 
the cylinder, and also between the platinum of the head and 
the platinum of the cylinder. Berthelot makes the joint 




Fig. 17. 




Fig. 20. 



tight with a smearing of vaseline around the opening, being 
careful not to have a trace on the inside. If no bubbles 
escape on putting it into the calorimetric bath, the joints are 
tight. 

The cover is pierced at the centre with a small hole, in 
which is fitted a tube formed of a hollow screw acting as a 
cock, and itself provided at the upper end with a circular 
head. The electric ignition is produced by a platinum wire 



50 



CALORIFIC POWER OF FUELS. 




Fig. 21. 



fitting in an opening of the removable conical cover E. This 
is prepared (Fig. 21) in advance, and is covered with a layer 
of gum lac applied in a strong alcoholic solution. When the 
first coat is dry, a second one is put on and 
dried in a stove. Berthelot says that the 
combination of these two coatings, one elas- 
tic and soft, the other hard and brittle, 
resists very well the enormous pressure on 
the cone. This cone, lightly greased, is put 
into the conical opening in the bomb cover, 
and screwed up tight by means of a nut. It 
is well to protect the base of the cone by a 
film of mica. 

An electric current passed through E 
L&J wj S (Fig- 2I ) reddens the spiral of very thin 
iron wire f placed between the platinum 
wires and one of the supports 6"5" of the cap- 
sule cc containing the substance m. This iron wire soon 
burns and kindles the combustible. 

Fig. 22 gives a general and complete internal view. 
The iron spiral is formed of an iron wire -^ millimetre 
(0.004 inch) thick, rolled up on a spindle. The wire may be 
weighed, or by using the same length of wire always have the 
same weight. 

The spiral is attached on one side to the cone, and on the 
other side by means of a platinum wire to the platinum sup- 
porting the fuel, taking care that the iron has no straight por- 
tions. The support of the capsule or platinum-foil is then 
fixed in the cover, by aid of the screw, arranging it so that 
the spiral is directly over the combustible used. The cover 
is put on, turning it gently to make the contact more perfect. 
The nut is tightened and the wire carefully screwed up, 
always using wooden tongs to prevent injuring the bomb. 

The form of the bomb is such as permits filling the calo- 
rimeter with the smallest possible quantity of water — a neces- 






BERTHELOT'S CALORIMETER, 



51 



sary condition that the temperature, and consequently the 
precision, attain a high degree. For solids and also for coal 
Berthelot uses bombs containing 400 to 600 cubic centimetres 
{24 to 37 cubic inches), placed in a calorimeter of 2000 grams 
(4.4 lbs.) of water. 

To determine the heat of combustion of coal, for instance, 




Fig. 22. — Berthelot Bomb. 

it must be previously reduced to powder in order to have a 
sample whose cinder is known. As all kinds of coal do not 
burn completely in this state, they are formed into pastilles,* 
which are weighed, and burnt. They are put on a platinum 
grating or foil, placed on the support vSS (Fig. 21), over 

*We obtain very resisting pastilles or briquettes from fat coals by- 
simple compression in a pastille or suppository mould such as used by 
druggists. With lean coals, or anthracite, the pastilles are too friable and 
burn incompletely. This is easily remedied by mixing with a small 
quantity of silicate of soda solution. Several of them should be made at 
a time, the cinders of some being determined to obtain a mean and the 
others burnt in the bomb. They may contain about 1 gram of pure coal. 



52 CALORIFIC POWER OF FUELS. 

which and in contact with it is the iron spiral. At the 
instant of lighting a slight noise is made, and soon the ther- 
mometer begins to rise, showing that the combustion is pro- 
ceeding. 

Compressed oxygen may be introduced either by a pump 
drawing the gas from a holder or by using a compressed-gas 
cylinder. In both cases the gas is used without drying, if 
the combustible contains hydrogen in quantity enough to 
saturate the gases formed with water produced by its combus- 
tion. But if, on the contrary, the combustible has little or 
no hydrogen, like wood-charcoal for instance, it is not im- 
material whether the oxygen be dry or not. In this case it 
is well to use the oxygen moist, or to put a little water in the 
bomb on the internal walls. By this means a correction for 
heat of vaporization of water formed by the combustion is 
obviated. 

Oxygen compressed to 120 atmospheres is nearly dry. 
Berthelot observes: "The oxygen is, in short, actually or 
nearly dry, and if it contains aqueous vapor the tension is 
reduced to one fourth or one fifth on account of the change 
in volume of the gas during its passage through the bomb. It 
may be nearly nullified by the cold produced at the instant of 
filling the bomb. This admitted, we shall have to account in 
most combustions for the evaporation of the water produced 
in the bomb; and this is from 2 to 3.5 calories in a bomb of 
\ litre (about 0.6 pint), or 5 to 6 calories in a bomb of 600 to 
700 cubic centimetres (37 to 43 cubic inches). These are 
rather small quantities, it is true ; but while they can be 
neglected in industrial tests, they cannot in rigorously 
scientific investigations. This correction may, however, be 
neutralized by putting into the bomb 4 or 5 cc. of water, 
which should be considered in the calculations. 

When oxygen not previously compressed is used and 
forced in by a pump, Berthelot recommends passing the gas 
through a large red-hot copper tube filled with oxide of the 



BERTHELOT'S CALORIMETER. 53 

same metal, so as to burn any oil which may have been taken 
from the pump. 

Operation. — At the laboratory of the College of France 
the successive operations are as follows : 

1. Light the fire to heat the oxygen red-hot; 

2. While the gas-holder is filling with oxygen, the fuel is 
dried ; 

3. Weigh the fuel; 

4. Place the fuel in the bomb ; 

5. Grease the cover slightly; tighten with the screw; 

6. Begin to compress the oxygen by forcing the air out 
with a few strokes of the piston ; pump slowly to prevent 
heating the pump ; 

7. Close the stop-cock of the pump ; break the connection 
with the bomb, extinguish the fire, and replace the bomb on 
its support so as to carry it to the calorimeter room ; 

8. Pour the water into the calorimetric bath. 

The apparatus is allowed to come to equilibrium, and the 
readings of the thermometer taken for five minutes. The 
iron coil is then heated by the electric current from a small 
bichromate battery. It takes fire and kindles the combustible, 
which generally burns without smoke or producing any car- 
bonic oxide, as Berthelot has shown.* 

The water condensed from the combustion contains small 
quantities of nitric acid, showing imperfectly purified gas. This 
may be determined by titration, if accurate results are sought, 
and calculated 0.227 calories per gram of HNO s . The cor- 
rection will be very small. A correction for the iron used 
may be made at the rate of 1.65 calories per gram, this being 
the heat of formation of the magnetic oxide. 

* With very fat coals it sometimes happens after a combustion that the 
platinum shows a black or brown mark, indicating a slight deposit of black 
or tar which hasescaped combustion. Occasionally, also, a trace of tar is 
found at the bottom of the bomb. These may be prevented by using a 
grating or perforated plate instead of the foil. This detail must be attended 
to with a new coal. 



54 CALORIFIC POWER OF FUELS. 

With substances containing nitrogen and sulphur, such as 
coal, the corrections are more complicated, as a larger quantity 
of nitric acid is formed and the sulphur forms sulphuric acid. 
If exactness is sought, it will not be sufficient to make a volu- 
metric test : the sulphuric acid must be determined separately. 
Generally, however, this estimation may be dispensed with, if 
for technical purposes only. When, on the contrary, ab- 
solutely correct figures are desired, both acids must be con- 
sidered. In the calculation the nitric acid is reckoned as 
0.227 calorie per gram and the sulphuric acid as 1.44 calories 
per gram. 

But these two corrections are really unimportant even 
with coal, as it contains usually only about I per cent of 
nitrogen or sulphur. One per cent of nitrogen represents 4^- 
per cent of HN0 9 , or 10 calories; one per cent of sulphur 
represents 3 per cent of H a S0 4 , or 43 calories, — both quite 
small compared with 7000 to 8000 calories. 

Below will be found the details of a complete combustion 
taken from Berthelot's work. 

HEAT OF COMBUSTION OF CARBON. 

The wood charcoal, purified by chlorine at red heat to 
remove all traces of hydrogen (Favre and Silbermann's 
method), is dried at 120 to 140 C. (248 to 284° F.), then 
weighed in a closed tube after cooling in a sulphuric acid 
desiccator. 

0.437 gram carbon; cinders, 0.0028 gram (0.66 per cent); 
real carbon, 0.4342 gram. 

Preliminary Period. 



o minute i7.36o c 

1st " I7-366 

2d " 17.360 



3d minute 17.360° 

4th " 17.360 



BERTHELOT'S CALORIMETER. 55 



Combustion. 



5th minute. 18.500' 

6th " 18.782 



7th minute 18.820' 

8th " 18.818 



Subsequent Period. 



9th minute 18.810 

10th " 18.802 

nth " 18.795 



12th minute 18.785' 

13th " 18.775 

14th " 18.768 



Initial cooling per minute, 

Af = 0.00 . 
Final cooling per minute, 

Atn = + 0.008 . 
Correction for cooling, 

At = + 0.056 . 
Variation of temperature, uncorrected, 

18.818 - 17.360 = 1.438 . 
Value of corrected temperature, 

1.438° + 0.056°= 1.484°. 
Value in water of the calorimeter (including oxygen), 

m = 2398.4. 
Weight of acid formed ; 
HNO3 = 5 cc. of ^0 normal KHO = 0.0173 gram. 



S 6 CALORIFIC POWER OF FUELS. 

Total heat observed, q x = 3.5562 calories. 

Heat of iron coil, 22.4 ) 

" "o.. 73 HNO„ 3.9} *=ff^3 " 
Real heat due to the carbon, 3.5299 " 

3. 5299 

or for one gram, = 8.1206 calories, 

0.4342 

or per kilogram, 8129.6 calories, 

or 14871.0 B. T. U. per pound. 



CHAPTER VI. 

THE CALORIMETRIC BOMB ADAPTED TO 
INDUSTRIAL USE BY MAHLER. 



THE calorimetric bomb of Berthelot costs considerably 
more than can be paid by an industrial laboratory, owing to 
its large amount of platinum. Mahler replaced the interior 
platinum of the bomb by an enamel deposited on the steel. 
The description given by him in his paper before the Socie'ti 
cT Encouragement de Paris, in June, 1892, is as follows: 

The apparatus is shown in Fig. 23. It consists essen- 
tially of a steel shell, B, capable of resisting 50 atmospheres 




Fig. 23. — Mahler Calorimeter. 

and 22 per cent elongation. This quality was carefully chosen, 
not only on account of the pressure it must stand, but also as 
it aids the enameling. The metal is very pure, containing but 

57 



53 CALORIFIC POWER OF FUELS, 

little phosphorus or sulphur. Tensile strength tests are the 
best criterion of quality. 

It has a capacity of 654 cc. (40 cubic inches) at 15 C. It 
is gauged with a balance showing g oo Tr- The total weight 
is about 4 kilograms (8.8 lbs.) with the accessories.* The 
metal of the walls is 8 millimetres (about 0.3 inch). 

The capacity is greater than Berthelot's, and has the ad- 
vantage of insuring perfect combustion of carbon in all cases, 
due to a certain excess of oxygen, even when the purity of 
this gas as bought is not quite satisfactory. Besides, it is 
designed to study all industrial gases, even those containing 
a large percentage of inert gas ; hence it must be able to use 
a sufficiently large quantity to generate the required tempera- 
ture. The contraction at the top aids in enameling. 

The shell is nickeled on the outside, while internally it 
has a coating of white enamel, resisting corrosion and oxidiz- 
ing action of the combustion. f It does not, however, offer 
resistance to the heat, being very thin, and it weighs only 
about 20 grams (308 grains). 

It is closed by an iron stopper made tight by a lead washer 
(P, Fig. 33) and clamped down. This carries a conical-seated 
stop-cock, R, of fine nickel — a metal almost unoxidizable. 
An electrode well insulated and reaching the interior by a plat- 
inum wire runs through the stopper. 

Fig. 24 shows most of the details. 

Another platinum wire, also fixed on the cover, supports 
the platinum disk or foil on which the fuel is placed. 

The calorimeter, the non-conducting material, the support 
for the shell in the water, and the agitator differ in numerous 
details from those of Berthelot, and are much cheaper. 



* Slight modifications have been made in the dimensions of the metal of 
the bombs made lately by Golaz. 

\ Prof. W. O. Atwater finds that the enamel chips off in time, and that 
after about 300 combustions it requires re-enameling. Hempel for coal 
determinations uses one without any inside enamel. 



MAHLER'S CALORIMETER. 



59 






The calorimeter is of thin brass, and is quite large on ac- 
count of the size of the combustion-chamber. It contains 
2200 grams (4.85 lbs.) of water, thus eliminating the causes of 
error due to the loss of a few drops by evaporation,* The 
agitator of Berthelot is supplanted by a very simple and gentle 
cinematic combination called a drill 
movement, and which can be worked 
without fatigue. The source of elec- 
tricity is a Trouve bichromate pile (P, 
Fig. 23) of 10 volts and 2 amperes. 

The oxygen used is that furnished by 
the Compagnie Continent ale d' Oxygene. 
This company supplies oxygen free from 
CO a , but containing from 5 to 10 per 
cent of nitrogen. This means of supply 
simplifies the manipulation ; it also ob- 
viates the introduction of grease, as 
happens with oxygen compressed by a 
pump in the laboratory. f 

The cylinders vary in size, and con- 
tain gas at a pressure of 120 atmospheres. 
The average content is about 1200 litres 
(about 40 cubic feet) compressed. They FlG - 24> 

have a uniform top, and hence the copper pipe connecting the 
bomb with the manometer and the cylinder, once adjusted, 
will fit all of them. 

The method of working is very simple. 

Weigh 1 gram of the substance to be tested in the cap- 
sule. Fasten a small weighed iron wire (English gauge 26 or 
30) to the electrode and to the support of the capsule. Put 
the end in the bomb and fasten in the cover, which should be 
held in a vise. Put the conical stop-cock in connection with 
the oxygen cylinder, and open it carefully so as to allow suffi- 

* The evaporation never exceeds a gram per hour, 
f This gas is also compressed by pumps at the works. 




60 CALORIFIC POWER OF FUELS, 

cient oxygen to pass in for the required pressure. Close the 
cock of the oxygen cylinder, carefully close the conical cock, 
and break the connection between the bomb and the oxygen 
cylinder. The substance, especially if coal, must not be too 
fine, and the oxygen must flow in very slowly to avoid blow- 
ing any of it from the capsule. 

The bomb thus prepared is placed in the calorimeter, and 
the thermometer and agitator adjusted. Pour in the previously 
weighed water, agitate a few minutes to restore equilibrium of 
temperature, and commence the observations. 

The experimenter notes the temperature minute by minute 
for four or five minutes, and determines the rate of the ther- 
mometer before the combustion. Then he joins the elec- 
trodes, and the combustion begins immediately, almost instan- 
taneously; but the transmission of heat to the calorimeter 
takes some time. 

The temperature is taken one-half minute after kindling, 
then at the end of the minute, then at each minute to the 
time when the thermometer begins to lower regularly. This 
is the maximum. The observations are continued for a few 
minutes more to ascertain the rate of fall of temperature. 

We now have all the elements needed for the calculation, 
and particularly for the single correction necessary to make 
under the circumstances. This is the correction for loss of 
heat before reaching the maximum temperature, which is 
quite small considering the short time and the large mass in- 
volved. 

It is not necessary to use the corrections of Regnault and 
Pfaundler with this apparatus. Newton's law of cooling gives 
sufficiently accurate results, even in rigorous investigations. 
Special experiments made to determine the rate of cooling of 
the water in the calorimeter, when the apparatus was set up as 
usual, showed that the correction may be regarded as follow- 
ing a simple law, but between comparatively large limits, 



MAHLER'S CALORIMETER. 6 1 

even under a variation of several hundred grams in amount of 
water used. 

The law* is 

i. The decrease in temperature observed after the maxi- 
mum represents the loss of heat of the calorimeter before the 
maximum and for a certain minute, with the condition that 
the mean temperature of this minute does not differ more than 
one degree from the maximum. 

2. If the temperature considered differs more than one 
degree but less than two degrees from the maximum, the 
number representing the rate of decrease dimminished by 
0.005 will be the correction. 

The two preceding remarks suffice in all cases with Mah- 
ler's apparatus. The variation of heat in the first half-minute 
after kindling may also be corrected by the same law. 

The agitator must be worked continually during the ex- 
periment, being careful of the thermometer. 

When through, the conical valve is opened and then the 
bomb. Wash the inside with a little distilled water to collect 
the acids formed. The proportion of acids carried away by 
the escaping oxygen at the opening may be neglected. De- 
termine the acids volumetrically. 

When experimenting with substances low in hydrogen and 
incapable of furnishing sufficient water to form nitric acid, it 
is advisable to put a little water in the bomb, or hyponitric 
acid would be formed. 

All the data being obtained, we proceed to the calculation 
of the calorific power Q. 

Let A be the observed difference of temperature ; 
a, the correction for cooling; 
P, the weight of water in the calorimeter; 
P , the equivalent in water of the bomb and acces- 
sories; 

* It is evident that the rule must be modified for apparatus notably dif- 
ferent from that used by Mahler. 



62 CALORIFIC POWER OF FUELS. 

p, the weight of the nitric acid, HN0 3 ; 
p', the weight of the iron ; 
0.23 calorie, the heat of formation of 1 gram of nitric acid ; 
and 1.6 calories, the heat of combustion of I gram of iron. 
We then have 

Q = (J + a)(P+ />') - (0.23/ + 1.6/O. 

In testing coal in this manner the small amount of sul- 
phuric acid formed will be reckoned as nitric acid without 
serious error, as it will be very small. The heat of the reac- 
tion is 1.44 calories per gram of H a S0 4 formed. 

The above details apply to liquids as well as solids. Heavy 
liquids, such as the heavy oils, tars, etc., are weighed directly 
into the capsule ; but light, easily vaporized liquids must be 
placed in pointed glass bulbs. These are put into the capsule, 
and just before closing the bomb are broken to allow access 
of the oxygen to the liquid. An almost perfect combustion 
is obtained in operating with a great variety of materials, 
nothing but cinders remaining. 

To determine the calorific power of gases the exact con- 
tent of the bomb must be. known. Fill it first with gas. 
Then work the air-pump to reduce the pressure to several 
millimetres of mercury, and then fill the bomb again with gas, 
under atmospheric pressure and at the laboratory temperature. 
The bomb may then be considered full of pure gas. 

The method of working with gases is the same as with 
solids or liquids. The operator must not forget the need of 
preventing too great dilution with oxygen, as then the mix- 
ture will cease to be combustible. With illuminating gas 5 
atmospheres of oxygen is sufficient, and with producer gas 
only one-half atmosphere, as shown by the mercury gauge, is 
needed. 

The gases to be burnt are kept in gas-holders over water 
saturated with gas, or over salt water, according to circum- 



MAHLER'S CALORIMETER. 63 

stances, and are saturated with aqueous vapor when they enter 
the bomb. From the calorific capacity of the different parts 
we obtain that of the whole, the glass and enamel being 
omitted. 

Soft steel 3945 grams. 3945 X 0.1097 = 432.76 

Brass 545 " 545XO.093 = 50.68 

Mercury, plati- 
num, and lead 72 * J2 X 0.03 = 2.16 






Sum 485.60 grams. 

The coefficient 0.1097 is the one adopted by the College 
of France, from Berthelot and Vielle's experiments, for a steel 
of similar quality. We have given above (page 14) the 
calculations relative to the valuation in water. By direct 
method of mixing water of different temperatures Mahler 
found the equivalent to be 470 and 484, and assumed the 
mean 481. 

By the method of burning a body of known composition 
and heat of combustion he obtained with naphthalin 9688 
calories — within Yinru °^ that given by Berthelot (9692). 

The equivalent in water may also be obtained by burning 1 
gram of known composition and heat of combustion — naph- 
thalin for instance.* We may also, after Berthelot, burn a sub- 
stance of fixed composition at two trials with different weights 
of water in the calorimeter. Two equations are thus formed, 
from which the heat of combustion of the body used is elimi- 
nated, and the heat sought obtained. 

In using naphthalin care must be taken to weigh it only 
after being gently fused in the capsule. It is so light that if 
not agglomerated some would be blown away by the oxygen. 
In practice the tests are made rapidly. The water equivalent 
once determined may be verified by combustion of cane- 

* This practical method has the advantage of automatically eliminating 
causes of error. . . 



64 CALORIFIC POWER OF FUELS. 

sugar (C„H n O u ), for which Berthelot and Vielle found 3961.7 
calories. (Use 2 grams for a combustion.) 

Examples of Calculations. 

Mahler gives several types of calculations from his notes, 
so as to show the different circumstances which may occur. 
A. Colza Oil. — Elementary analysis showed — 

Carbon 77.182 per cent. 

Hydrogen 1 1.7 11 " " 

Oxygen and nitrogen 11. 107 *' " 



100.000 



Weight taken, 1 gram. Calorimeter contained 2200 grams 
water. Equivalent in water of bomb, etc., 481 grams. 
Pressure of oxygen, 25 atmospheres. 

The apparatus prepared as above was allowed to rest a 
few minutes to gain equilibrium of temperature. Then com- 
menced noting the temperatures. 



minute 10.23 

1 " 10.23 

2 minutes 10.24 

Rate of variation, 



Preliminary Period. 

3 minutes io.24 c 

4 " IO.25 

5 " IO.25 



IO.25 — 10.23 

a. = - — = 0.004 . 

5 
The electrodes are connected and the combustion begins. 

Combustion Period. 

5^ minutes 10. 8o c 

6 " 12.90 



7 minutes.. 13.79 

8 " .. 13.84 maximum.* 



* Prof. Jacobus recommends plotting the temperatures and using, not 
the maximum, but the one at the instant the curve of cooling becomes a 
straight line. The difference is slight, but important in some cases. 



MAHLER'S CALORIMETER. 6$ 

Period after Maximum. 



9 minutes I3-82 C 

10 " 13.81 

11 " 13.80 



12 minutes I 3-79° 

13 " I3-78 



Rate of variation after maximum is 

13.84-13.78 
a t = = 0.012 . 

5 

The thermometer observations now stopped. 
The gross variation in temperature was 

13.84- 10.25 = 3-59°- 

The corrections are as follows : 

The system lost during the minutes (7, 8) and (6, 7) a 
quantity of heat corresponding to 2a t . 

2a t = 0.012 X 2 = 0.024 . 
In the half-minute (5J, 6) it lost 

i(a t — 0.005) = O.0035 . 
But during the half-minute (5, 5^-) it gained 



0.004 

2<2 = = 0.002 . 



Consequently, the loss for the minutes (5, 6) is 
0.0035 — 0.002 = 0.0015 . 



66 



CALORIFIC POWER OF FUELS. 



So that the system had lost, before reaching the maximum 
temperature, 

0.024 + 0.0015 = 0.0255, 

which must be added to the 3. 59 already found, making the 
variation in temperature 3.61 5 , neglecting the 4th decimal. 
The quantity of heat observed, then, is 

Q = (2200 + 481)3.615 = 2681 X 3.615 = 9.6918 calories. 

From this number must be subtracted — 

1. The heat of formation of the o. 13 

gram of HNO3 0.13 X 0.23 = 0.0299 

2. The heat of combustion of 0.025 

gram of iron wire 0.025 X 1.6 = 0.04 



Total subtraction 0.0699 

The final result is, then, 

9.6918 — 0.0699 = 9.6219 calories, 

or for I kilogram 9621.9 calories, equivalent to 1 73 19.4 B.T.U. 

TECHNICAL EXAMINATION OF COAL. 

The coal taken was a sample of Nixon's coal from South 
Wales. 



Preliminary Period. 



minutes, degrees. 

15.20 

1 15.20 

2 15.20 

3 15-20 



Combustion. 



minutes. 
3\ 
4 
5 
6 



degrees. 
16.60 



17.92 

1S.32 

18.34 

maximum 

oxygen pressure 25 

atmospheres 



After Combustion. 



minutes. 
7 
8 

9 
10 
11 



degrees. 
18 32 
18.30 
18.30 
18.30 
18.26 



18.34 — 18.26 



= o.oi6 { 



MAHLER'S CALORIMETER. &7 

Difference of gross temperature . 3. 140 

Correction (4, 5) (5, 6) 0.016 X 2 0.032 

(4, 3i).- 0.005 

(3. 3i °- 000 



Corrected difference of temperature 3. 177 

or 3 .i8°. 

Calories. 

Heat disengaged 3. 18 . 3.18 X 2.681 = 8.5256 

Iron wire 0.025. 0.025 X 1.6 =0.04 

Nitric acid 0.15. 0.15 X O.23 =0.0345 

0.0745 



For one gram 8 .45 1 1 

or 845 1. 1 for 1 kilogram, equivalent to 152 12 B. T. U. 



EXAMINATION OF A GAS. 

Illuminating gas was examined under the following con- 
ditions :* 

Barometric pressure 761 mm. (29.6 inches). 

Tension of aqueous vapor 8 " (0.314 inch). 

Temperature of laboratory 18. 5 C. (65. 3 F.). 

Volume of bomb 654 f cc. (39.9 cubic inches), 

" dry at 0° and 760 mm. 

606 cc. (37 cubic inches). 



< < i i 



The capsule was left in its usual place in the bomb to pre- 
vent specks of iron oxide from dropping on the enamel and 
injuring it. 

* See Kroeker's calorimeter on page 73. 
f Exactly 653.9 cubic centimetres. 






68 



CALORIFIC POWER OF FUELS. 



Preliminary 


Period. 




minutes. 


degrees. 


O 


18 


8o 


I 


18 


8o 


2 


18 


8o 


3 


18 


8o 


4 


18 


8o 


a = 


o.o 


o 



Combustion. 



minutes, degrees. 
4i 19-50 

5 20.00 

6 20.08 

7 20.81 
maximum 



After Combustion. 




= 0.006° 



Remarks. 



Pressure of oxygen 
5 atmospheres 

grams. 
Nitric acid. . . . 0.06 
Iron wire 0.025 



Gross difference of temperature, A 1.28 

Correction as usual, a o 015 



Difference, A -\- a 1-295° 

Calories. Calories. 

Quantity of heat observed, i. 295° 1.295X2.681= 3.47189 

Heat of HNO3 formation 0.06 X 0.23 =0.0138 

Heat of iron-wire combustion 0.025 X 1.6 = 0.04 

0.0538 



Heat of combustion of 606 cc. at o and 760 mm 3.41809 

or per cubic metre at 760 mm. 5640, or 633.6 B. T. U. per cubic foot. 

COMBUSTION USING AN AUXILIARY SUBSTANCE. 
Sometimes an unconsumed residue is left while determin- 
ing the heat of combustion of some difficultly burning sub- 
stances, diamond or graphite for instance. In this case a 
combustible auxiliary is used to obtain complete burning of 
the sample. The most convenient to use is naphthalin (C 10 H 8 ), 
the heat of combustion of which is exactly known, 9692 cal- 
ories. 

Take petroleum coke, which is nearly allied to graphite. 
It is mixed with a little naphthalin which has been previously 
melted at a low heat and then cooled. After cooling the 
weight of the naphthalin is taken. 
The coke analyzed as follows: 

Carbon 97.855 per cent. 

Hydrogen 0.489 

Oxygen 1.196 " 

Nitrogen..: 0.260 " 

Ash 0.200 " " 



100.000 



MAHLER'S CALORIMETER. 
The data obtained are as follows: 



6 9 



Preliminary- 
Period. 



minutes, degrees, 

22.05 

1 22.05 
5 22.04 



a Q = — 0.002 



Combustion. 



minutes, degrees, 
5-J 22.6o 



24.20 
25.02 

25.13 
25.14 
maximum 



After 
Combustion. 



minutes, degrees. 
IO 25.12 
14 25.05 



at = 0.015 



Remarks. 



grams. 

Napthalin 0.034 

Iron wire 0.025 

Nitric acid 0.080 

Water of calorimeter. 2200. 
Equivalent in water.. 481. 



Difference of temperature 25.14 — 22.04 = 3'ioo c 

Correction for minutes (9, 8), (8, 7), (7, 6). . 0.015 X 3 = 0.045 

" i minute (5£, 6) = 0.005 

" i " (5, 5i) =0.001 



Corrected temperature difference 3. 151' 



Then, 

Total heat developed 3. 15 3.15 X 2.681 = 

From this subtract 

Heat due to naphthalin 0.034 X 9692 = 0.3295 

" " " iron wire 0.025 X 1.6 = 0.04 

" " HNO3 0.08 X 0.23=0.0184 



Heat developed by the combustion of the coke, 
•or 8057.2 per kilogram, or 14503 B. T. U. 



8.4451 



0.3879 



.0572 



When the combustible tested contains hydrogen, it must 
be remembered that, while the gas in the bomb is dry at the 
beginning, it is saturated at the close of the experiment. In 
reality, the latent heat of vaporization of the small quantity 
of water necessary to be added is inconsiderable. The mean 
of several tests was 5 in 8500 calories observed, or only 
yrfVg-. Still, when we test gases, which cause less marked 
difference in temperature than solids or liquids, we must allow 
for this heat of vaporization to be exact. 

It may be asked if any allowance will be made for the 
heat of the electric current at the moment of kindling. The 



70 CALORIFIC POWER OF FUELS. 

heat developed by a current with intensity / and electro- 
motive force E is 

4-17 

t being reckoned in seconds. If t was appreciable, this should 
be considered at least in exact determinations. But, actually, 
t is very small ; the contact is hardly established before the 
iron is burnt and the contact broken.* 

Mahler cites two successive tests made on the same coal 
with his bomb and with the bomb of the College of France, 
as furnishing proof of the accuracy of his method. 

The following results were obtained : 

Scheurer-Kestner 

at the Mahler. 

College of France. 

Coal (pure) from Bascoup, Belgium 8828 8813. 

The calculations may be rendered simpler and the obser- 
vation more rapid, still being exact enough for industrial uses. 
Take the equation 

<2 = {A + a)(P+ P) - (0.23/ + 1.6/), . . (!) 

arranging the terms in order of the corrections 

a = J{P + P) + a(P+P) - (0.23/ + 1.6/). (2> 

It is clear that the calculation of the calorimetric operation 

* In exact researches this heat can be easily determined if wished. It 
will be sufficient to measure the electromotive force in volts. Then put 
an amperemeter in the line which connects the bomb and kindle the com- 
bustible as usual. The displacement of the needle shows the intensity of 
the current under the conditions of the test, and also the time during which 

EI 

the current was closed. The formula 1 will give the quantity of heat 

4.17 

sought. 



ATWATER'S CALORIMETER. 7 l 

reduces to the determination of a maximum and to one multi- 
plication if we have 

a(P+P') = o.zy> +1,6/ (3) 

Now from the tests made we readily see that whatever 
value a may take, it increases with the quantity of heat gen- 
erated in the bomb ; it is a little greater when the external air 
is warmer than when it is cooler — a fact which may be attrib- 
uted to the influence of evaporation on the cooling of the 
bath.* 

On the other hand, the nitric acid appears to increase with 
the quantity of heat generated, and tends to offset the cor- 
rection from a. In short, p' is, within certain limits, at the 
control of the observer, same as P . We consider it then 
possible to arrange once for all so as to have the expression 
(3) sufficiently close for industrial purposes. 

This can be done with Mahler's apparatus. Thus for oil 
of colza the multiplication A{P -\- P) gave 9625 calories, 
which is within 3-^-0 of the final number obtained after all 
corrections ; with the Nixon's coal we found t ;at A{P -\- P') = 
8418 calories, which differed ^-^ from the correct number; 
with coal-gas the product 2681 X 1.28 = 3432 calories, while 
the corrected result was 3418, or ¥ ^ difference. 

atwater's calorimeter. 

Prof. Atwater has considerably modified the bomb, so 
that it seems to have some advantages for easy working. 
Fig. 25 gives a sectional view of it in the calorimeter. The 
steel used is the same as that used in the Hotchkiss guns, 

* The rapidity of cooling in the apparatus employed by Mahler was, 
according to experiments, between 15 and 20 C. 

dB 

~ = o.oo5(T-To), 

To being the temperature at which cooling ceases. 



72 



CALORIFIC POWER OF FUELS. 



and having an unusually high tenacity, seems admirably fitted 
for the purpose. A represents the bomb, C the screw-cap, 
B the cover, which is placed on the bomb cylinder and held 
down by the screw-cap. " The cover is provided with a neck 
into which fits a cylindrical screw E, holding another screw H. 
On the side of the neck is an aperture G, between the lower 
end of D and the shoulder. In D is a washer of lead, on 
which the lower edge of E fits. By opening or closing the 
screw F the narrow passage from z is opened or closed. The 
opening is used for admitting oxygen at a high pressure 
through a narrow passage to charge the bomb. In B is an 
aperture through which passes the platinum wire J7, which is 
separated from the metal of the cover 
by insulating material. Hard vulcan- 
ized rubber serves very well for this 
purpose. Fastened to the lower side 
of the cover is another platinum rod, /, 
between which and H an electrical con- 
nection is made with a very fine iron 
wire. A screw-ring holds the small 
platinum capsule, in which the sub- 
stance to be burned is placed. At KK 
are ball-bearings of hard steel to avoid 
friction in screwing the cap down." 

" The large cylinders N and O are 
made of indurated fibre, and covered 
with plates of vulcanized rubber. A 
stirrer serves for equalizing the temper- 
ature of the different portions of water 
Fig. 25.— Atwater Bomb. after the combustion is completed." * 

The thermometer used is by Fuest 
of Berlin, graduated to y-j^ degree, and can be read with a 
magnifying-glass to yoVo degree. 

*Prof. W. O. Atwater, in Bulletin No. 21, U. S. Dept. of Agriculture, 
1895, pages 124 and 126. 




KROEKER 1 S CALORIMETER. 



73 



The apparatus has been used with success in making the 
very numerous determinations made by Atwater on the heats 
of combustion of food-products and other allied organic sub- 
stances. 



kroeker's calorimeter. 

Kroeker has recently modified the bomb, making two in- 
let channels instead of one. By this means he has a current 
of oxygen gas passing in at one opening and waste gases 
passing out at the other. It can thus be used for the same 
purpose that a Junker calorimeter is used, and it is claimed 
with just as satisfactory results. 

The cylinder (Fig. 26) is bored out of a piece of Martin 
steel, and has a closely-fitting screw-plug for cover, the depth 
of the screw joint being 25 mm. The walls 
of the cylinder are 10 mm. thick; external 
diameter, 72 mm. ; internal diameter, 52 
mm. ; height, 120 mm. ; contents, 200 cc. 
It has four small legs on the under side, 
which support it and keep it entirely sur- 
rounded by the water of the bath. The 
entire inside surface is enameled, or prefer- 
ably platinized. The fuel, in the form of 
compressed cylinders weighing one gram, 
is put into the carrier, ignited as usual, 
and the combustion gases collected and 
examined. 

He also has a method of heating the 
calorimeter bomb in an oil-bath so as to 
expel all the water of combustion and hy- 
dration. He thus obtains data for cor- 
rections due to the usual method of determining the water, 
i.e., considering the water as condensed. 




Fig. 26. — Kroeker 
Calorimeter. 



74 



CALORIFIC POWER OF FUELS. 



WALTHER-HEMPEL BOMB. 

Two modifications of the Berthelot bomb are known 
under this name. The larger one does not differ in enough 
points to make a special mention of it necessary; but the 
smaller one, the one intended for use in analysis, is worthy of 
description. 

It consists of a small cylinder of 33 cc. capacity (Fig. 27), 
bored out of white cast iron and enameled inside. The walls 
are 2 millimetres thick, and it is strong enough to resist eight 
times the pressure generally used. The cover 
is fastened on by means of a screw-clamp, 
and through it passes the slanting opening a y 
having the electric wire-carrier insulated by 
a caoutchouc sheath. To the wire at the end 
of this sheath is attached a platinum wire for 
kindling the combustible. On the opposite 
side of the cover is the oxygen tube d. The 
platinum wire c is attached to the under side 
of the cover, and supports the combustible- 
carrier and its little fire-clay cylinder e. 

The fuel is made into small cylinders by 
compression, put into the fire-clay cylinder, 
and ignited by the electric spark. The 
products of combustion are collected and 
weighed or measured : the water partly in the 
bomb and partly by means of a calcium chlo* 
ride tube ; the nitric and sulphuric acids are 
determined by titration with -^-^ normal alkali, 
and afterwards separated if deemed necessary. It is claimed 
to be capable of use the same as a large one. A full descrip- 
tion of it is given in the Berliner Bericht for January, 1897. 




Fig. 27. 

Walther- 

Hempel Bomb. 



CHAPTER VII. 
SOLID FUELS. 

COAL. 

AMONG the first careful tests ever made, to determine the 
heat value of different kinds of coal, are those made in 1843 an d 
1844 by Prof. W. R. Johnson for the U. S. Navy. He 
analyzed and tested all the kinds obtained from the United 
States and England, which were then in use by the navy. 
At the time they were made the calorimetric determinations 
were not considered as of the importance they are now, 
and his tests were limited to determining the evaporative 
power of the coals. Mr. W. Kent reviewed them in the 
Engineering and Mining Journal, 1892, and showed that up to 
the time of the experiments nothing comparable with them 
had been attempted, and that in many respects they compare 
favorably with work done to-day. 

In 1857 Morin and Tresca made numerous determina- 
tions of the calorific power of coal and wood, and in 1853 
they published a work on " Fuels and their Calorific Power, " 
in which they make many recommendations for more accurate 
work. They wrote: " It would be extremely important if 
experiments with the calorimeter could be made on most of 
the fuels, by methods similar to those used by Favre and Sil- 
bermann." 

In 1868 such experiments were made by Scheurer-Kest- 
ner, and continued by him later with the aid of Meunier- 
Dollfus. They based their calculations on pure coal, i.e., with 
moisture and ash deducted. This method, which has been 

75 



j6 CALORIFIC POWER OF FUELS. 

followed by many others, seems very logical, as it facilitates 
comparison of different fuels by reducing them to the same 
basis. Enormous errors due to comparison of values not 
comparable are thus obviated. Coal having 5 per cent im- 
purity has been compared with coal having only 1 per cent, 
no account being made for the difference, and of course very 
erroneous and misleading deductions obtained. 

It is a simple task for the engineer or the workman even, to 
determine approximately the proportions of moisture and ash 
as given on the grate. Knowing these proportions and the 
heat of combustion of the pure coal, they can render a state- 
ment of the practical working. If, on the contrary, the ex- 
perimenter is limited in such way that he neglects the com- 
position of the coal, it is impossible to make a conjecture as 
to its intrinsic or comparative value; still less can he judge of 
it as a steam generator. 

In 1879 Bunte made some experiments at Munich, using a 
special apparatus devised by him for the occasion, which 
was part calorimeter and part boiler. The tests were pub- 
lished in Dingier' s Polytechnisches Journal. Some of the 
results are included in the tables of this book. 

Since then numerous tests have been made on nearly all 
the known coals. A collection of all available ones from 
which the desired data could be obtained will be found far- 
ther on. 

The question as to the actual evaporative effect of each 
coal can be settled only by actual tests made on the boiler 
intended for use, as the same coal will give slightly different 
results with different kinds of boilers ; also, and in a more 
marked degree, with different methods of firing and handling. 
The results in the tables cannot be taken, then, as absolute 
for all boilers under all circumstances, but they can be 
depended on for comparison of the different fuels with the 
same boiler and under proper conditions. 

The manner in which a coal acts under heat in a closed 



SOLID FUELS. 



77 



vessel is a most important indication, taken in connection 
with its elementary composition. Gruner gave his opinion 
that the real value of a coal could be determined better from 
its proximate than from the ultimate composition. Speaking 
of the Loire coal, he says : 

" The proximate analysis, which consists in distilling coal 
in a retort and incinerating the residue, allows direct valu- 
ation of the agglomerating power as well as the nature and 
proportion of the ash. Further, it is easy to show, especially 
with the aid of the work of Scheurer-Kestner and Meunier- 
Dollfus, that the calorific power varies with the proportion of 
fixed carbon left by distillation. This is true at least for all 
coal properly so called, but not always true for anthracite 
and lignite." * 

Gruner formed the following table based on the quantity 
and nature of the coke furnished and the calorific power. He 
held, from the results of S.-K. and M.-D., that if the heat 
value of a coal increases with the proportion of fixed carbon 



Classes or Types 

of Coal 
properly so called. 



i. Dry coals with | 
long flame, f 

2. Fat coals with \ 

long flame (gas V 
coals), ) 

3. Fat coals, prop-] 

erly so called I 
(" blacksmith " f 
coals), J 

4. Fat coals with j 

short flam e V 
(coking coals), ) 

5. Lean coals or J 

anthracite, j 



Per Cent 

Coke to 

Pure Coal. 



55 to 66 
60 to 68 

68 to 74 
74 to 82 
82 to 90 



Per Cent 

of 

Volatile 

Matter 

in 

Pure Coal. 



45 to 40 



40 to 32 



32 to 36 



26 to l£ 



Nature and 

Appearance 

of Coke. 



{Powdery or 
slightly 
coked, 
f Completely 1 
I agglomer- j 
-j ated, often- \ 
I er caked, [ 
(.but porous. J 

Caked and 

ore or less 

puffy. 



( Caked and ) 
■< more or less > 
I puffy. | 



( Coked, I 
( compact. ) 

f Slightly 
,' coked, 
I oftener 
[ powdery. 



CalorificPower, 
Actual. 
Calories. 



8000 to 8500 
8500 to 8800 

8800 to 9300 
9300 to 9600 
9200 to 9500 



Industrial 

CalorificPower. 

Water at o° 

Vaporized at 

112 per Kilo of 

Pure Coal 

Burnt, 

in Kilograms. 



6.7 to 7.5 
7.6 to 8.3 

8.4 to 9.2 
9.2 to IO 
9.0 to 9.5 



* Annales des Mines, 1878, vol. IV. 



7$ CALORIFIC POWER OF FUELS. 

or coke formed, this increase is produced gradually by cutting 
off the lean coals and dividing the fat coals into three classes 
— gas, forge, and coking. 

Bearing on the advisability of having proximate analyses, 
as well as ultimate analyses of coal, is the question recently 
brought up by Mr. Kent, regarding the ratio of hydrogen and 
carbon in coal. In discussing the results of Lord and Haas' 
determinations of Ohio and Pennsylvania coals, he thought he 
had discovered the ratio, that the fixed carbon is nearly equal 
to the total carbon minus five times the available hydrogen in 
bituminous coals, and minus three times the hydrogen in 
semi-bituminous ones. He gave a table showing results 
which support the hypothesis. 

LIGNITE. 

From an industrial standpoint lignite is of considerable 
importance. It occurs in most countries, and is used in a 
great many for domestic and manufacturing purposes. 

As a fuel it is inferior to coal, being less distantly 
removed from woody fibre, and hence contains more hydro- 
gen and, usually, considerable water. Most of the latter, 
however, dries out on exposure to the air. In some cases 
as much as 40 or 50 per cent of water is found in the 
freshly mined lignite, of which at times 20 per cent remains 
when air-dried. This greatly affects its value as fuel ; still 
it is used in many of the Western States, and also in 
Europe. In some European localities, when thoroughly 
dried and compressed into blocks, especially in Italy and 
Austria, it is used as fuel for producing gas and for evapo- 
rating, with good results. In Austria it is burnt without 
any preparation, except drying in the air for heating salt- 
pans. 

The amount of ash varies exceedingly, being in some 
cases as low as 0.9 per cent, and in others as high as 58 per 



SOLID FUELS. 79 

cent. It even varies in the same locality and in the same 
bed. In burning lignite there is considerable loss in the waste 
gases on account of the large quantity of air introduced, and 
also from the moisture carried off from the fuel. 

Brix published the following results with dried lignite : 

Water Evap- Per cent 
orated. Ash. 

Lignite of Aussig, Bohemia 5.8 pounds 15.0 

" Perleberg, " 5.6 " 6.0 

" " Goldfuchs n. Frankfort... 5.5 " 9.1 

" Rauen 5.4 " 6.3 

Bunte used two kinds of lignite in boiler-tests, and gives 
the following results : 

Neusattel. Chodan. 

Calories in steam 42.8 49.2 

" ''gases 19.6 21.0 

" li aqueous vapor 9.2 8.7 

" "ash 9.0 6.1 

" unaccounted for 19.4 15.0 

The grate used was a step grate (Treppen-Rost). 

The lignite used on the railways in Italy contained 15 
per cent of water, and gave a yield of heat equal to one half 
its weight of coal. 

Analogous to the lignites are certain shales or fossils 
carrying bitumen. They are sometimes termed boghead 
cannel, bituminous schist, etc. They are distilled in some 
localities for oil, but are not much used as fuel. 

Bunte determined the heat of combustion of a sample 
from Australia, and analyzed one from Scotland. 

Carbon. Hydrogen. O + N. Calories. 

Boghead shale, Australia. 83.17 10.04 6.79 9134 
Scotch Boghead 8 1. 54 11.62 6.84 



8o CALORIFIC POWER OF FUELS. 

Scotch Boghead generally contains 18 to 24 per cent of 
ash. From its analysis as above, its heat of combustion 
should be near that of the other one given. 

PEAT. 

Peat is formed by the agglomeration of vegetable d^bris t 
and retains a large amount of water, which will not separate 
without heat. Its composition varies but little from that of 
wood, the principal difference being less oxygen and more 
carbon. 

The composition may be represented by — 

Carbon 60 

Hydrogen 6 

Oxygen and nitrogen 34 

100 
The heat of combustion is lower than that of coal or 
lignite, as might be expected. The quantity of hydrogen 
exceeds that necessary to form water with the oxygen. 

It is usually dried before using, and when dry becomes 
quite porous. It carries, however, in this state some 10 to 
15 per cent of water, which can be expelled only by artificial 
means. Large quantities of it are converted into charcoal in 
special kilns, and, where the large amount of ash is no objec- 
tion, it makes a good fuel. It cannot be used for metallurgical 
purposes on account of its friability. From 30 to 40 per 
cent of its weight is left in the charcoal as carbon, but at the 
same time the ash increases to 15 to 25 per cent, and even 
more. This consists principally of phosphates and sulphates, 
with very little carbonates ; hence it is not as apt to clinker 
as other fuel ashes. 

Brix obtained with peat an evaporative power of 5.1 1 
pounds of water. . The peat used was from Flatow, and 
contained 10.7 percent of ash. Another, from Buchfeld-Neu- 
langen, contained 1.2 per cent of ash, and gave 5.12 pounds 



SOLID FUELS. 5 1 

evaporated. Noury, using a special grate, obtained from the 
Alsace peats 4 to 5 pounds evaporation (ashes deducted). 

Bunte analyzed the gases produced by the combustion of 
peat on the hearth of a salt-pan, and found, carbonic acid 13, 
oxygen 6.4, nitrogen 80.6. 

Karsten says that 2-J pounds of peat are equal to one of 
coal. In some experiments made at St. Petersburg a fire- 
grate of 32 square feet and 696 square feet of boiler heating 
surface was used. The peat was compact, hand-moulded into 
4-inch balls, and dried till moisture did not exceed 14 per cent. 
4.26 pounds of coal were evaporated for 1 of peat. 

Crookes and Rohrig, in their " Metallurgy," say: "One 
pound of dry turf will evaporate 6 pounds of water. Now in 
I pound of turf, as usually found, there are f pound of dry 
turf and \ pound of water. The j- pound can evaporate 4 J 
pounds of water; but out of this it must first evaporate the J 
pound of water contained in its mass, and hence the water 
boiled away by such turf reduces to 4J pounds. The yield 
is here reduced 30 per cent, a proportion which makes all the 
difference between a good fuel and one almost unfit for use. 
When turf is dried in the air under cover it still retains -^ of 
its weight of water, which reduces its calorific power 12 per 
cent; I pound of such turf evaporates 5 -J pounds of water." 

COKE. 

Coke usually met with is from three sources : from gas- 
coal, and made in gas-retorts; from gas or ordinary bituminous 
coal, and made in special ovens; from petroleum, and made 
by carrying the distillation of the residuum to a red heat. 

Coke from gas-works is usually softer and more porous 
than the other kinds, burns more readily, but does not give 
as intense a heat. It has been used considerably for domestic 
heating, and in factories where a high heat is not needed 
but where a smokeless fuel is desirable. The oven coke is 
usually in large columnar masses of a close texture and quite 



82 



CALORIFIC POWER OF FUELS. 



hard. It has a dead gray-black color and is not susceptible 
of polish. It is principally used in furnaces requiring a 
blast, although limited quantities of it have been used in 
domestic heating, for which purpose it must be broken up 
much finer than its usual size. Petroleum coke is generally 
in large irregular lumps, perforated with cavities of greater or 
less size, the interior of which is usually quite smooth and 
shining. Its color is blacker than that of gas or oven coke, 
and its hardness intermediate. It is used principally for mak- 
ing electric carbons, although considerable quantities are used 
for fuel. 

With the exception of gas-coke very little use is made of 
this fuel for steaming, the fire being too intense locally, and 
hence very apt to burn out the boiler directly over it. In all 
cases plenty of air is needed to keep up the combustion, which 
is also a drawback for steaming purposes. For metallurgical 
furnaces it is different. Here it is almost the ideal fuel, giv- 
ing an intense reducing heat at just the part of the furnace 
where most needed. It has been used in iron furnaces for 
years, and is still the favorite fuel. It is superior to anthracite, 
as it has no tendency to splinter and crack with the heat, and 
bears its burden very well. Of course this does not apply to 
ordinary gas-coke, which crushes easily. 

Coke is essentially carbon, and the mineral portions of the 
coal from which it is made. It contains small quantities of 
hydrogen and nitrogen, as may be seen from the tables. The 
percentage of these, however, is very low, so that the cal- 
culated and observed heat-units are usually within the limits 
of error, as is shown in the following table : 



Name. 



Saarbruck 

Petroleum coke 
Graphite 



c. 


H. 


N. 


Loss. 


Calories 
observed. 


Calories 
calculated. 


98 .04 

98.05 
98.98 


0.73 
0.50 
0.02 


O.25 


I.23 
I.20 


8200 
8057 
7901 


8229 
8151 
8054 



Authority. 



Bunte 

Mahler 

Berthelot 



SOLID FUELS. 



83 



WOOD CHARCOAL. 

Wood charcoal always contains quantities of hydrocarbons 
which have resisted the action of heat. That called forest 
charcoal, made by burning in heaps, is the most charged with 
them ; that obtained from distillation of wood in retorts con- 
tains less. 

The heat of combustion is very variable. According to 
Berthier* commercial wood charcoal contains 10 per cent of 
volatile matters and 2 per cent of ash (carbon 80 to 90, hy- 
drogen 1.5-4). 

Pure wood charcoal was first tested calorimetrically by 
Favre and Silbermann, and since then by several experi- 
menters. To obtain it pure it was calcined strongly and 
treated with chlorine to remove all traces of hydrogen. In 
this state wood-charcoal produces under constant pressure 
8080 calories, F. & S., or 8100 S.-K. & M.-D. ; with con- 
stant volume Berthelot and Petit obtained 8137 calories. 

Several years ago Berthier pointed out that half-burnt 
charcoal, charbon roux or Rothkohle, was superior in combus- 
tible content to that perfectly burnt. Sauvage has confirmed 
this, and gives the following results: 



100 lbs. of wood I 
charred for ) 



Weighed 

100 cu. ft. measured 



3 hours. 



65.4 lbs. 
86 cu. ft. 



4 hours. 



53.O lbs. 
76 cu. ft, 



5 hours. 



47.O lbs. 
58 cu. ft. 



5^ hours. 



41.5 lbs. 

55 cu. ft. 



6£ hours. 



39.I lbs. 
52 cu. ft. 



Mound 
Charcoal. 



17.2 lbs. 
33 cu. ft. 



and 
cubic foot wood contained of combustible matter 908 parts. 



3 hours' heating " 

4 " 

5 " 

5* " 



H 



charcoal 



883 
904 

"33 

1091 

1136 
1069 



* Traite des essais par la voie seche, vol. i, p. 2S6. 



84 CALORIFIC POWER OF FUELS. 

So that the amount of combustible matter does not increase 
after 5 hours' heating, and a continuance of the heat diminishes 
it. 

The principal use of charcoal is in iron furnaces, where it 
has been used for years, and produces the highest grades of 
iron, being free from sulphur and phosphorus. A small 
amount is used in private dwellings and hotels for heating 
and cooking. For boiler heating it has been used only 
experimentally. 

Scheurer-Kestner and Meunier-Dollfus experimented with 
it in boiler-heating and found very little combustible gas in 
the products. Beech charcoal was used, and an evaporative 
effect of 7.62 pounds of water was obtained. The waste 
gases contained: 

Carbonic acid 11.16 per cent. 

Carbonic oxide °-37 " 

Oxygen 8.72 " 

Nitrogen , 79-75 " 



100.00 



Brix, using wood and peat charcoal, obtained the follow- 
ing results: 

Wood charcoal 7.55 pounds evaporated. 

Peatcharcoal 6.85 

Schwackhofer burnt charcoal from hard and soft wood in 
his calorimeter and obtained (constant volume) 7140 calories 
for the soft charcoal and 7071 calories for the hard. The 
charcoal in both cases was the ordinary unpurified charcoal as 
sold. 

WOOD. 

Wood consists of a compact tissue more or less hard, 
formed of cellulose and a so-called incrusting substance. 






SOLID FUELS. 85 

Wood contains, besides, small quantities of mineral matter and 
hygroscopic water varying from 15 to 30 per cent, according 
to dryness. Air-dried, it contains about 15 per cent of water, 
which it gives up easily on exposure to a heat of ioo° C. 

The composition of wood may be represented by the 
following : 

Carbon. Hydrogen. Oxygen. Ash. Water. 

Wood dried at ioo° 49.5 6.0 43.5 1.0 0.0 

" " in the air 29.6 4.8 34.8 0.8 29.0 

Regarding wood from its ultimate composition, we may 
consider it as a hydrate of carbon, that is, as carbon united to 
water, the proportion of hydrogen and oxygen being nearly 
the same as in water. But regarded from its proximate com- 
position, it is entirely different. What has been said of soft 
coal can be repeated for wood ; that, those having a similar 
ultimate composition behave differently in distillation in a 
closed retort and produce very different proportions of carbon 
(as charcoal) ; hydrocarbons, liquid or gaseous ; acid products, 
resin, and tar. It was supposed that the heat of combustion 
differed also, and this has been verified by experiments. 

Berthelot and Vielle determined the heat of combustion of 
cellulose, and found 680 calories for the molecular weight of 
wood, or about 4200 calories per kilogram. 

Hard wood gives less heat than soft wood. According to 
Gottlieb's experiments, pine-wood has a heat value of 5000 
calories, while oak gave only 4620 calories. Mahler's exper- 
iments confirm a difference in favor of pine, but in less pro- 
portion. 

Two determinations made by Mahler are (cinders and water 

deducted) : 

Fir. Oak. 

Carbon 51.08 50.43 

Hydrogen. .. = ... . 6.12 5 .88 

Oxygen with trace of nitrogen. ... 42.90 43-69 

100.00 100.00 

Heat of combustion 4828 4689 



S6 



CALORIFIC POWER OF FUELS, 



Gottlieb obtained the following numbers, using a calo- 
rimeter of constant pressure, in which he burnt 2 grams of 
wood in the space of two or three minutes. The composition 
of the gas produced was not determined ; he was satisfied 
that he had perfect combustion, and his figures do not appear 
very far from the truth. For cellulose he obtained 4155 
calories. 



Name. 



Oak.. 
Ash.. 
Elm.. 
Beech 
Birch. 
Fir... 
Pine., 



c. 


H. 


N. 


O. 


Ash. 


Calories. 


50.16 


6.02 


O.09 


43-36 


0-37 


4620 


49.18 


6.27 


O.07 


43-91 


0.57 


471 1 


48.99 


6.20 


O.06 


44-25 


O.50 


4728 


49.06 


6. 11 


O.09 


44.17 


0-57 


4774 


48.88 


6.06 


O. IO 


44.67 


O.29 


4771 


50.36 


5-92 


O.05 


43-39 


O.28 


5035 


50.31 


6.20 


O.04 


43-o8 


0.37 


5085 



8316 
8480 
8510 

8591 
8586 
9063 
9153 



Gottlieb's results are 69 calories less than Mahler's for oak 
and 207 more for fir. 

In burning wood for steaming the fire is easily controlled; 
combustion is more complete; the products of combustion 
contain only very small quantities of unburnt gases ; and the 
ashes are generally free from carbon. The countries using 
wood for this purpose are growing less in number yearly, on 
account of improvement in transportation and the discovery 
of new coal seams ; petroleum oils for fuel have also become 
more common, especially in Russia, the United States, and 
Canada. 

Morin and Tresca, in their tests, found that one pound 
of wood was equivalent to 0.368 pound of coal. Scheurer- 
Kestner's experiments in 1 87 1 show results more favorable 
for wood. The wood used was Vosges fir, which had been 
piled under cover for half a year. A cubic foot weighed 
19.76 lbs. It was burnt in the same boiler used in his 
previous experiments, with the result that 1 pound of wood 
evaporated 4.4 pounds of water. The ratio was 0.490, or 
nearly one half that of Ronchamp coal. 



SOLID FUELS. 87 

Brix made a number of experiments in using wood for 
heating, and found that dry pine gave the best results — 5 
pounds per pound of fuel. Elm gave 4.6 pounds; birch, 
4.6; oak, 4.56; ash, 4.63; and beech, 4.47. 

Wood should be dry as possible, as otherwise it has to 
furnish heat to vaporize, not only the water formed from its 
hydrogen, but also that already existing as moisture. We 
have seen that this loss with coal is considerable, it is still 
greater with wood. Suppose the wood to be ordinary air-dried, 
containing 20 per cent of water. If this wood, when per- 
fectly dry, could evaporate 5 pounds of water, it now has 
only £ of that power, or power to evaporate 4 pounds; but it 
already carries \ of its weight of water, which must be vapor- 
ized. Hence the available power is 4 pounds less \ pound = 
3| pounds, or j6 per cent of its dry value. Hence the 
economy of using only dried, and even artificially dried, wood. 



CHAPTER VIII. 
LIQUID FUELS. 

SHALE-OILS.— PETROLEUM. 

THE mineral oils comprehend the liquid hydrocarbons 
extracted from bituminous schist or coal and its congeners by 
distillation, as well as the oils which exist already formed in 
the earth, and called by the special name of petroleum. 

While the former are seldom employed in heating, petro- 
leum has become an important fuel in the countries which 
produce it. Its special qualities, light weight, and low price 
per calorie compared with other fuels insure a great future. 
The knowledge of its heat of combustion has become, then, of 
considerable interest. 

Its ultimate percentage composition varies within rather 
close limits, yet it is of a very complex proximate composi- 
tion. The industry of refining crude petroleum extracts from 
it some 50 per cent of refined oil for use in lamps, and hav- 
ing a density of 45 to 47 Beaume, boiling-point 170 C. 
(328 F.); 10 per cent of naphtha with a lower density and 
boiling-point ; and 20 per cent of paraffin oil of a higher den- 
sity and boiling-point. 

Crude petroleum contains a large number of hydrocarbons 
of the general formula C w H 2w+2 , and running from CH 4 to 
C 19 H 34 , with many isometric modifications. The industrial 
treatment modifies it profoundly. Hydrocarbons containing 
95 per cent of carbon have been found in the products of 
distillation.* 

*Wurtz, Dictionnaire de Chimie, Supplement. 



LIQUID FUELS. 89 

The first calorimetric experiments were published by Ste.- 
Claire Deville in 1868 or 1869, using a large calorimeter 
especially constructed for the work. Mahler used the bomb. 
The liquids were burnt in the bomb under nearly the same 
conditions as solids, when they had no appreciable vapor ten- 
sion. When they had considerable vapor tension (light oils, 
for instance) Berthelot placed them in a closed vessel, the 
bottom being platinum and the top formed by a pellicle of 
gun-cotton. 

Heating by oil is quite recently introduced, but is 
already developed to a high degree in Russia and on this 
continent, and is gaining in other localities. The small 
volume occupied in comparison with its high calorific power 
renders it a formidable competitor with coal. 

To burn petroleum, atomizers fed by steam or compressed 
air are used. They generally consist of a horizontal pipe un- 
der the boiler, fed with oil from an elevated reservoir placed at 
a presumably safe distance. The steam enters inside the oil- 
pipe, and, mixing with the oil, throws it into a spray and pro- 
duces a flame several feet long. At the Chicago Exposition 52 
tubular boilers were exhibited heated by oil, developing a 
power of 25000 H.P., and yielding a total evaporation of 12000 
cubic feet per hour. The oil used was the heavy portion of 
petroleum (the lighter ones having been distilled off for 
illumination), and it was fed under a pressure of one-fourth 
atmosphere. The result was an evaporation of about 15 
pounds of water per pound of oil. 

In 1889 Albert Hubner ran a whole battery of boilers 
with oil at his works in Moscow. He used Baku Nafta, or 
"Mazoute," which contained carbon 86.3, hydrogen 13.6, 
and oxygen o. 1 per cent. The density was 0.910 to 0.914. 

At Petrolea and Oil City, Canada, the heavy residuum 
from the stills is used as fuel under boilers and stills. The 
burners used are very simple, and run without producing 
smoke. In the United States, the Standard Oil Company has 



90 CALORIFIC POWER OF FUELS. 

pushed the sale of fuel-oil made of Ohio crude, and large 
quantities of it have been used ; large quantities of a special 
grade are also made for use in enriching water gas. 

The calorific power of petroleum residuum is, according 
to Sainte- Claire Deville, 11460 calories (20628 B. T. U.), 
the evaporation at 5 pounds pressure being 15 pounds. This 
compared with the heat of combustion shows a useful effect 
of over 86 per cent, while the entire absence of smoke, un- 
burnt gases, ashes, and irregularity in air-supply add to its 
advantages still more. 

Some experiments made at the Hecla Engineering Works, 
Preston, England, and lasting two days, used a marine boiler. 
The first day natural draft was used, the second a Korting 
blower. The oil was blast-furnace oil from Sheffield, and 
contained: 

Per cent. 

Carbon 83.54 

Hydrogen I 0-59 

Oxygen 5-94 

Sulphur 0.09 

100. 16 

By Thompson's calorimeter its value was 16080 B. T. U. 
Equivalent to water at 2 12 °F 16.66 pounds. 

The results were: First day, 14.97 lbs. ; second day, 14.21 
lbs., — a yield of 89.87 and 85.25 per cent of the theoret- 
ical. 

A series of tests made at South Lambeth with a Cornish 
boiler showed 20.8 lbs. evaporation; average of several days, 
19.5 lbs. The same boiler with the best Aberdeen coal 
yielded 6.5 lbs., — an advantage of 3 to 1 in favor of the 
oil. 

The following analyses of the waste gases from boilers using 
oil show how perfect the combustion is, and that little if any 
excess of air is needed : 



LIQUID FUELS. 9 1 

CO, 14.19 18.08 

CO 5.20 0.34 

O 0.78 0.34 

Hydrocarbons.... 1.30 None. 

H Not determined. None. 

N 78.53 81.24 

To have the best results, the burner must be so regulated 
as to have a flame bordering on, but not quite, smoky. Thus 
sufficient and not too much air is obtained, The quantity of 
steam needed to atomize the oil at Moscow is 4 per cent of the 
water evaporated. The use of compressed air has been tried 
in some places with very satisfactory results : the atomizing 
is good, but the cost is higher, and the probable chemical 
effect of the steam is wanting. 

Nothing but a bare mention need be made of animal and 
vegetable oils, as they are not used in the arts for heating 
purposes except, perhaps, on very exceptional occasions. 
The calorific power of all of them is high, as may be seen 
from Table I. 



CHAPTER IX. 
GASEOUS FUELS. 

The heat of combustion of gaseous combustibles has been 
determined for a great many compounds, definite and pure. 
That of the industrial gases has been determined by different 
operators and in different ways, with more or less happy 
results. Its determination is often one of the greatest com- 
mercial interest, since it is used in domestic heating as well 
as in industrial appliances, where it is necessary to obtain 
definite, regular working. It serves also to furnish motive 
power to gas-engines, in which the heat of combustion is not 
without importance. Finally, it is well to know the heat 
produced in air or water-gas apparatus, if we wish to reach 
the best condition for their production and use. 

For heating steam-boilers gas has given good results and 
a very high evaporative effect. It is easily regulated, and 
thus any required heat can be produced by simply turning a 
valve. No smoke is generated, no soot or deposit of any 
kind produced in the flues, and no ashes to take out of the 
ash-pit. The fireplace needs repairing but seldom, and 
the boiler is heated evenly and regularly, there being no 
danger of burning out in strongly heated spots, as no such 
spots exist. 

In metallurgical furnaces, gas possesses a decided advan- 
tage in its long, clean, easily managed, intense flame, and this 
advantage has been long recognized. A flame of 25 feet or 
more in length is easily produced, and it is practically uniform 
for its whole extent. Part of the heat usually lost up the 
chimney can be utilized to heat the air-supply, and no more is 
supplied than just enough for perfect combustion. 

Using gas as fuel enables the metallurgist to use poor 

92 



GASEOUS FUELS. 95 

grades of coal, and all variations in quality may be eliminated, 
a uniform product being had by storing the gas in a holder, or 
by making proper arrangement of different generators so that 
an average will be obtained. In several cases where hand-fed 
coal fires have been tried against fires burning gas from the 
same coal, better results have been obtained, due to the possi- 
bility of more closely adjusted regulation. The tests made 
at Brieg may be cited. Here each boiler had 141.25 square 
feet of heating-surface and steam-pressure 6 to 7 atmospheres. 
No. 1 boiler was hand-fired ; No. 2 was, gas-fired. The 
evaporation in pounds per pound of fuel was: 

No. 1 8.34 8.74 8.28 4.02 2.569 2.764 

No. 2 9.86 9.73 10.07 5-44- 3-251 3-I58 

Increase... 18$ 12$ 20$ 35$ 25$ 14^ 



HEAT OF COMBUSTION OF GASES FROM ANALYSIS. 

When the chemical composition of a gas is known exactly, 
its heat of combustion can be correctly calculated ; but in 
absence of a correct analysis, the calorimeter must be used. 

Knowing the proximate composition of a combustible 
gas, that is, the proportion of chemically defined components 
as well as their heats of combustion, it is sufficient to add the 
numbers obtained for each constituent gas. Take, for 
example, the analysis of illuminating gas of Manchester as 
given by Bunsen: 

Hydrogen. 45-58 

Marsh gas (CH 4 ) 34-90 

Carbonic oxide 6.64 

Ethylene (C 2 H 4 ). 4.08 

Butylene (C 4 H 8 ) 2.38 

Sulphydric acid 0.29 

Nitrogen ..., 2.46 

Carbonic acid.. 3.67 



100.00 



94 CALORIFIC POWER OF FUELS, 

The calculation is as follows : 



Components. 



Hydrogen 

Marsh gas, CH 4 

Olefiant gas, C 2 H 4 

Butylene, C4H H 

Carbonic oxide 

Sulphydric acid, H 2 S.. 



No. of Litres per 
Cubic Metre. 



455. 

369 

40. 

23- 

66. 

2. 



Weight per Cubic 
Metre at o° and 
" mm. 
Grams. 



70- 



89.61 
715.58 
1251.94 
2503.88 
1251.50 
2551.99 



Total calories per cubic metre 



Heat of 

Combustion per 

Cubic Metre. 



3066 

9340 

I4980 

29042 

3057 
1 1400 



Calculated 
Calories. 



1395 

3169 

6ll 

690 

20I 

33 

6099 



City of Manchester gas, as analyzed by Bunsen, gives, 
then, with complete combustion, 6099 calories per cubic 
metre (685 B. T. U. per cubic foot). 

If, however, only the actual ultimate composition of the 
gas is known or the total percentage of carbon, hydrogen, 
oxygen and nitrogen, then the calculated result will differ from 
the experimental one. This is because the heat units of the 
elements added together do not make those of the compound, 
as the heat of combination of the different constituent gases 
is not allowed for. If this factor is known, then it can be 
used as a correction and the correct heat determined. 

This heat of combination of the elements to form the 
component gases will be seen in comparing the calculated and 
the actual heat of combustion of the following gases : 



Gases. 



Marsh gas. . 
Olefiant gas. 
Acetylene. . 
Benzene . . . . 



Formulae. 


Carbon. 


Hydro- 
gen. 


Calculated 
Heat. 


Actual 
Heat 


CH 4 

C2H4 

C2H2 

CeHs 


75- 
85.7 
92.3 
92.3 


25. 
14.3 

7-7 

7-7 


14685 
11859 
IOTI4 
IOII4 


13343 
I2I82 
I2I42 
I24IO 



Differ- 



+ 1342 
~ 323 

— 2028 

— 2296 



It will also be seen, that although two gases may have the 
same percentage composition of the elements, yet the heat of 
combustion may be different owing to the action of the various 
physical forces at work in molecular condensation, etc. 



GASEOUS FUELS. 95 

COAL GAS. 

The heat of combustion of illuminating gas obtained from 
the distillation of coal in closed retorts is very variable. It 
depends not only on the nature of the fuel, but also on the 
rapidity of the distillation and the heat by which it is accom 
plished. The heat of combustion varies from 5200 to 6300 
calories per cubic metre. It cannot be represented by any 
average number. 

According to Witz, at the same gas-works and with the 
same fuel, yields may occur from 4719 to 5425 calories. 
According to Bueb-Dessau, the illuminating gas of the same 
city during the same day will, sometimes vary 20 per cent. 
Dr. Birchmore reports the same result from his examinations 
of the gas of Brooklyn, N. Y. 

We are not certain that the composition assigned to coal 
gas by analysis corresponds always to the gas as obtained by 
distillation; in Europe, especially, a portion of the heavy 
hydrocarbons is taken out for sale separately, and the deficiency 
supplied by cheaper oils. 

From several, experiments which he made, Bueb-Dessau"* 
thought that the heat of combustion of illuminating gas was 
directly proportional to the candle power; but in addition to 
this being opposed to the theory of heat, the experiments of 
Aguitton show the contrary. He concluded from his deter- 
minations that each illuminating gas of different candle power 
has a definite heat of combustion which corresponds to the 
intensity of the light. His experiments were carried on with 
more than a hundred samples, rich and poor, the former kind 
from cannel coal, the latter from the end of the run carried to 
an extreme. He represents by the following formula the 

* Bueb-Dessau cites the following among others: 

Candle-power. Heat-value. 

Gas of Dessau 14. 4400 calories 

Gas of Bremen 21.9 5977 

Gas from cannel coal 26.0 6559 



g6 CALORIFIC POWER OF FUELS. 

relation between candle power and heat of combustion of a 

gas: 

c = t X 35 2 - 6 + 2280, 

in which c represents the heat of combustion and i the candle 
power. The formula seems to be applicable only between 
limits at which it has been verified — from 5 to 15 candles. 
Aguitton's determinations were made with the calorimetric 
bomb. 

The following table gives a rtsumt of his observations : 

r a\~ r>~ - Heat of Combustion 

Candle Power. per Cubic Metre> 

5 « 4043 

6 4395 

7 4748 

8 5 101 

9 5453 

10 5806 

11 6158 

12 65 1 1 

13 6864 

14 72 16 

15 7569 

7c(5q — 404.3 

'-^—^ — — = 352.6, coefficient adopted. 

The three samples of illuminating gas, analyzed and burnt 
in the bomb by Mahler and given in the table below, call for 
the following observations : Gas from Niddrie cannel coal, the 
most calorific per cubic metre is the least calorific per kilo- 
gram, because the density is greater than that of the other 
two. The richest in hydrogen by volume (Lavillette) is the 
poorest in calorific power per cubic metre, while the poorest 
in hydrogen by weight is the richest in calories per cubic 
metre. These are due to the low density of hydrogen, which 






GASEOUS FUELS. 



97 



is less calorific by volume than the other hydrocarbons occur- 
ring in illuminating gas. 







Analysis by Weight. 


Heat of C 


ambustion 




6 

u 

•a 




<u 










Name. 




>> 

C u? 


c 

V 


JO 






2 

<! 



2£ 

£3 


I 8 
S 


S 
a 

bio 






>> 


c 


hX) 






f,^ 


^T3 






'35 
c 




-a 






.0 


tXTJ 


u^ 


M 




<u 








rt 


K rt 


u 






Q 


u 


E 


U 


U 







PL, 


Niddrie cannel. . 


0.6367 


43-33 


13-50 


16.84 


9.26 


14.96 


6365 


7735 


Commentry coal. 


. 4046 


43-74 


21.46 


24.96 


7.08 


.5-75 


5834 


1 1 TOO 


Lavillette gas. . . 


O.4033 


42.25 


21.34 


21.23 


6.83 


8.33 


5602 


IO764 



A cubic metre of hydrogen develops 3091 calories in 
burning; a cubic metre of marsh gas develops 10038 calories; 
a cubic metre of olefiant gas, 15250 calories. 

GAS OF GASOGENES. 

The gasogenes, instead of transforming the fuel into car- 
bonic acid and water in a single combustion, produce this 
change in two distinct burnings, the first being to make a 
combustible gas and the second to burn this gas with air. 

In the first furnace, the coal, for example, is burnt in such 
a manner by feeding with an insufficient supply of air that a 
gaseous mixture is produced, containing principally carbonic 
oxide, besides nitrogen from the air. As the combustion has 
been well or poorly managed, it contains a less or greater 
quantity of carbonic acid, the production of which is avoided 
as much as possible. This is done by giving to the fuel only 
just enough air to form carbonic oxide, and not enough to 
form carbonic acid, even partially, and by making the bed of 
fuel quite deep. 

The heat produced by this combustion is not used, and 
consequently an important part of the calories of the coal is 
lost. Gasogene gas is then lower in calories, and inferior to 
coal gas, as commonly made by distillation. 



gS CALORIFIC POWER OF FUELS. 

One kilogram of carbon burnt to carbonic oxide disen- 
gages 2489 calories, while 1 kilogram of carbon burnt to car- 
bonic acid generates 8137 calories. There is lost, then, in 
burning carbon to carbonic oxide in a gasogene about 30 per 
cent of the available calories. 

At first sight this method of working seems irrational, but 
for obtaining high temperatures there are practical advantages, 
whose importance far exceeds the loss of heat in the gaso- 
gene. It permits much more elevated temperatures, and the 
recovery of a large portion of the heat, which in direct sys- 
tems of heating in high temperature furnaces passes to the 
chimney as complete loss. There is actually an economy in 
the ordinary metallurgical methods even with this loss. 

By means of gasogenes, we produce three kinds of gaseous 
fuel : the gas called producer or air gas, formed by the incom- 
plete combustion of the fuel, with production of a mixed gas 
containing carbonic oxide and hydrogen compounds ; the gas 
called water gas, from the decomposition of water by carbon at a 
high temperature, with production of carbonic oxide, hydrogen, 
and hydrogen compounds; and the gas called mixed gas, 
from the mixture of the two preceding ones by a process 
which combines the production of the two gases in the same 
furnace. 

PRODUCER OR AIR GAS. 

We have said that air gas results from incomplete com- 
bustion, and that its formation causes a loss of one third of 
the calories resulting from the complete combustion of the 
fuel. These gases contain, naturally, the nitrogen of the air 
used, to which must be added that of the air necessary to 
change the carbonic oxide and the hydrogen to carbonic acid 
and water. 

The heat of combustion and the composition determined 
by different experimenters varies considerably, showing that 
they did not always work with average samples. 



GASEOUS FUELS. 99 

The proportion of nitrogen in these gases reaches 56 to 
60 per cent; that of carbonic oxide, 21 to 32 percent; that of 
of hydrogen, from traces to 17 per cent. The theoretical 
calculation for the combustion of carbon in air to a gas con- 
taining only carbonic oxide and nitrogen gives for the first 
34.7 and for the second 65.3 per cent. 

By adopting for the composition of air the round numbers 
79 and 21, and for the weight of oxygen 1.430 grams per 
litre, for carbon the atomic weight of 12, and for oxygen 16, 

12 : 16 = 1000 grams : 1333 grams. 

A kilogram of carbon needs, then, i-J kilograms of oxygen. 
A litre of oxygen weighing 1.430 grams, 1333 grams would 
occupy 932 litres. These 932 litres will give with carbon a 
double volume, or 1864 litres carbonic oxide. Multiplying 
932 litres by the coefficient 4.77 (see Table XIV), we obtain 
the volume of the air corresponding, or 4445 litres. The 
gases of combustion will be composed then of these 4445 
litres of air and the 932 litres of increase in volume, or 5377 
litres for 1 kilogram of carbon. The 4445 litres of air will 
contain (at 79 per cent) 3513 litres of nitrogen, or 65.3 per 
cent.* 

The calculation is more complicated when we have fuel 
containing hydrogen, as one portion of the oxygen disappears 
by its combination with the hydrogen to form water. Take 
for example, a coal containing 90 per cent of carbon, 5 per 
cent of hydrogen, and 5 per cent of oxygen. Suppose 1 
kilogram of this coal, under theoretical conditions, burnt in a 
gasogene, i.e., with perfect transformation of the carbon into 
carbonic oxide and no residues. This coal contains 900 
grams carbon, 50 grams hydrogen, 50 grams oxygen. 900 

* One pound of carbon requires 1.333 lbs. of oxygen; 1 cubic foot of 
oxygen weighs 0.08926 lb. ; 1.333 lbs. measure 14.93 cu. ft. These would 
give 2g.86of CO. 14.93 X 4-77 = 71.216, and 71.216 + 14-93 = S6.146, volume 
of gases of combustion. These contain 56.26 cu. ft. of nitrogen. 



IOO CALORIFIC POWER OF FUELS. 

grams carbon produce 2100 grams carbonic oxide, requiring 
1200 grams oxygen. 1200 grams oxygen occupy 839 litres. 
50 grams hydrogen produce 450 grams water, and require 
400 grams oxygen. These 400 grams oxygen occupy 279 
litres. But the coal itself contains 50 grams oxygen, occupy- 
ing 35 litres. 

We have, then, 839 + 279 — 35 = 1083 litres of oxygen 
required, and to calculate the amount of air needed multiply 
by 4.77. This gives 5163 litres of air needed for the incom- 
plete combustion of 1 kilogram of carbon. These 5163 litres 
contain 4080 litres of nitrogen. 

To obtain the total volume of gases produced by the 
incomplete combustion, we may add to the volume of the air 
introduced the volume due to the formation of carbonic oxide, 
and this is equal to the volume of the oxygen used, or 839 
litres. We have, then, 5163 + 839 = 6002 litres. But a 
quantity of oxygen has disappeared corresponding to the 
formation of the water, or 279— 35 = 244 litres (35 litres 
exists in the coal as above), and 6002 — 244 =5758 litres of 
gas produced by the incomplete combustion of 1 kilogram of 
coal. 

Now, then, 5163 litres of air contain 4079 litres of nitro- 
gen, which would form -~ f or 70.8 per cent of the total 

5758 

gas. All these numbers are at 0° and 760 mm. pressure.* 

Generally gasogenes contain less nitrogen, different causes 
producing diminution, among which are the use of a lower 

* One pound of coal would be 6300 grains carbon, 350 grains oxygen, 
and 350 grains hydrogen; 0.90 lb. carbon produces 2.1 lbs. carbonic oxide, 
and needs 1.2 lbs. oxygen; 1.2 lbs. oxygen occupies 13.44 cu. ft. ; 0.050 lb. 
hydrogen produces 0.450 lb. water, and needs 0.400 lb. oxygen, or 4.48 cu. 
ft. The 0.05 lb. of oxygen in the coal occupies 0.56 cu. ft. Then 13.44 -f- 
4.48—0.56=17.36 of oxygen required 17.36 X 4»77 = 82.81 cu. ft. of air, 
containing 65.41 cu. ft. nitrogen. Total gases, 82.81 -f- 13.44 ~~ 3-9 2 = 92.33 
total volume of gas, and 

6 5-4i 

— — = 70.8 per cent. 

92.33 



GASEOUS FUELS. IOI 

hydrogen coal than we have taken, and the decomposition of 
the fuel in the body of the furnace with a certain quantity of 
aqueous vapor formed during the combustion, or from the 
moisture in the air supplied. 

Mahler determined the heat of combustion of a sample of 
gas from the Follembray glass-house, and found its composi 
tion per volume, using coal from Bethune, to be: 

Marsh gas 2 

Hydrogen 12 

Carbonic oxide 21 

Carbonic acid 5 

Nitrogen 60 

100 
The heat of combustion calculated from its composition is: 

Marsh gas 0.02 X 10038 = 200.8 

Hydrogen 0.12 X 3091= 370.9 

CO 0.2 1 X 3043 = 639.0 



1210.7 

With the bomb he found 12 12 calories. 

WATER GAS AND MIXED GAS. 

Water gas is produced when water is decomposed at high 
temperatures by fuels containing but little hydrogen, such 
as anthracite, charcoal, or coke. Mixed with hydrocarbon 
vapors, added to enrich it, or which may have been dej6^?v 
posed with the aqueous vapor, it serves for the illuminat.vjp 
of a great number of cities, principally in America. But this 
is not its only use, as it is used for heating, and also for gas- 
engines. Mixed with producer gas, it has become a powerful 
means of heating, especially where high temperatures are 
wanted. 

Water gas contains but little nitrogen : this is its main 
distinction from producer gas, and that which gives it a 
special value from an economical heating point of view. 



102 CALORIFIC POWER 01 FUELS. 

We have previously stated (page 97) that during the 
combustion of carbon in a gasogene, there occurs a genera- 
tion of nearly one third of the total heat were the fuel com- 
pletely burnt. Besides this, the combustion produces a gas 
containing about one third its weight of combustible gas and 
two thirds inert gas (nitrogen), which is mixed with it. 

These are important causes of two sources of loss in 
calories. In an air-gasogene one third of the calories is lost, 
since the gaseous products give up most of their sensible heat 
before being used. The 66 per cent of inert gas carries off 
an enormous quantity of heat to the chimney, and thence to 
the open air. It was with the idea of regaining or stopping 
these losses, or at least a large portion of them, that water 
gas originated. 

Aqueous vapor and carbon, when submitted to a high 
temperature, produce carbonic oxide and hydrogen. Theo- 
retically these are free from nitrogen ; but there is always 
present a small percentage for various causes. In the air 
gasogene 12 kilogram of carbon and 16 kilograms of oxy- 
gen (atomic weights) unite to form 28 kilograms of carbonic 
oxide. On the other hand, 12 kilograms of carbon and 18 
kilograms of water form 28 kilograms of carbonic oxide and 
2 kilograms of hydrogen. Then 1 kilogram of carbon fur- 
nishes 2.5 kilograms of gas composed of carbonic oxide and 
hydrogen. 

One kilogram of hydrogen has a caloric energy of 29042 
Calories.* These calories represent also the quantity of heat 
necessary to decompose the water; in the case of the water 
gas gasogene they are formed by the carbon burnt. The 12 
kilograms of carbon will have to furnish, then, the calories 
necessary to decompose 18 kilograms of water; that is, 

2 X' 29042 = 58084 calories. 

* Water being considered as vapor. 



GASEOUS FUELS. 103 

But 12 kilograms of carbon, in burning, generate only 
12 X 2473 = 29676 calories. 

To decompose the water, then, there is a shortage of 
force of 

58084 — 29676 — 28408 calories 

for 2 kilograms of hydrogen, or 14204 calories for 1 kilo- 
gram. The heat must be furnished by an external source. 
In other terms, to gasify 1 kilogram of carbon there must be 
supplied 

14204 -f- 6 = 2367 calories. 

As may be easily seen, this operation absorbs much heat, 
and the combustion of the water gas can give only the calo- 
ries used at first in forming it. The heat necessary for the 
decomposition of the water is actually taken from that of the 
preparatory period of the air gasogene, which makes a loss of 
one third of the total calories. In burning the water gas 
made under these conditions we utilize a part of the heat 
which would have been lost by the air gasogene only. 

The decomposition of water by carbon is not as simple as 
would appear from the equation 

H 2 + C = CO + H 3 . 

The lower portion of the fuel of the gasogene undergoes 
ordinary combustion on account of air being present ; while 
in the upper portion the reaction takes place between the 
gaseous products formed in the lower portion and the heated 
carbon. The carbonic acid is then in contact with the heated 
carbon and is reduced to carbonic oxide : 

C-\ C0 2 = 2CO. 



104 CALORIFIC POWER OF FUELS. 

Thus, the reaction with the water would be 

5H 2 -f 3 C = 2CO, + CO + 10H ; 

carbonic acid being reduced to carbonic oxide in the final 
reaction, as in the case with the air gasogene. 

Nine kilograms of aqueous vapor and 6 kilograms of 
carbon produce I kilogram of hydrogen and 14 kilograms of 
carbonic oxide, that is, a mixed gas is produced containing 
about one half its volume of each gas. 

One cubic metre of hydrogen weighs 85.5 grams; one of 
carbonic oxide, n 94 grams. Then the volumes occupied by 
each gas would be 11.69 f° r hydrogen and II.13 for car- 
bonic oxide, or 51.23 per cent of hydrogen and 48.77 per 
cent of carbonic oxide. 

From the foregoing account, it will be seen that the inter- 
mittent flow is a cause of great loss of caloric in the working 
of the water gasogene ; but when a gas is wanted solely for 
heating at high temperatures, it may be obtained by a mixed 
system working continuously. The gasogene is filled with 
a mixture of air and steam, the air being employed in 
the proper proportion to keep up the heat necessary, or, in 
other words, to furnish by the combustion of part of the 
carbon, the number of calories necessary to the gasifica- 
tion of the other part. 

We have seen (page 103) that to gasify 1 kilogram of 
carbon 2367 calories were needed. To maintain the heat 
this quantity must be produced by the action of the air. 
Mixed gases are poorer than water gas, as they contain more 
nitrogen and carbonic oxide and less hydrogen. Theo- 
retically, we should attain the result of furnishing the heat to 
the gasogene necessary to maintain the temperature by sup- 
plying the steam sufficiently superheated ; a gas very poor in 
nitrogen would then be made. But the superheating of 
steam causes new losses of heat. 



GASEOUS FUELS. 



105 



NATURAL GAS. 

Natural gas has been known for thousands of years in 
Asia, on the Caspian Sea, where it has long been a feature in 
religious services, but it is only recently that it has become 
of any use to man and played any part in the fuel world. 

The natural gas output in the United States has attracted 
considerable attention since 1875, and especially since 1880. 
This gas always accompanies petroleum, although petroleum 
does not always accompany the gas. The wells are situated 
in various portions of New York, Pennsylvania, Ohio, 
Indiana, West Virginia, Kentucky, Tennessee, Colorado, Cal- 
ifornia, and on the Canadian side also in numerous locations. 

Natural gas is not of a constant or uniform composition, 
varying very much according to the locality from which it is 
taken. The individual constituent gases vary between wide 
limits, hydrogen at some places being almost wanting, while 
at others it is as high as 35 or 40 per cent. Marsh gas is in 
every case the principal constituent, but this runs down as 
low as 40 per cent in some analyses. Nitrogen is some- 
times absent, and when present in large amounts, it is suppos- 
able that the gas analyzed was contaminated with atmospheric 
air. 

The Ohio and Indiana fields yield gas of nearer a uniform 
composition than any of the others. The following table is 
typical : 



Hydrogen 

Marsh gas 

defiant gas 

Oxygen 

Carbonic oxide 

Carbonic acid . . . . 

Nitrogen 

Hydrogen sulphide 



Ohio. 



Fostoria 



92.84 
0.20 

0.35 
0.55 
0.20 
3.S2 
O.I5 



Findlay. 



I.64 
93-35 
o.35 
o.39 
0.41 
0.25 

3-4i 
0.20 



St.Mary 1 s 



I.94 
93.85 
0.20 
0.35 
O.44 
O.23 
2.9S 
0.2I 



Indiana. 



Muncie. 



2-35 
92.67 
O.25 
0.35 
0.45 
O.25 
3-53 
0.15 



Anderson 



1.86 

93-07 
O.47 
O.42 

0-73 
O.26 
3.02 
O.15 



Kokomo. 



I.42 

94.16 
O.30 
O.30 
0.55 
O.29 
2.80 
o. iS 



io6 



CALORIFIC POWER OF FUELS. 



In addition to difference in composition in different local- 
ities, the composition of the gas varies considerably from 
time to time in each well. This is shown by the following 
analyses made at different times within a period of three 
months from a well at Pittsburgh, Pa. : 



Hydrogen. 

Marsh gas 

Olefiant gas. . . 

Methane 

Oxygen 

Carbonic oxide 
Carbonic acid. 
Nitrogen 



1 


2 


3 


4 


5 


9.64 


14-45 


20.02 


26. t6 


29.03 


57-85 


75-16 


72.18 


65.25 


60.70 


0.80 


0.60 


0.70 


0.80 


O.98 


5.20 


4.80 


3.60 


5-50 


7.92 


2.IO 


1.20 


1. 10 


0.80 


O.78 


I. OO 


0.30 


I. OO 


0.80 


O.58 


O.OO 


0.30 


O.80 


60 


O.OO 


23.4I 


2.89 


O.OO 


0.00 


O.OO 



35. 92 
49.58 

0.60 
12.30 
0.80 
0.40 
0.40 
0.00 



The quantity of gas used daily in the town of Findlay, 
Ohio, in 1890, was estimated by Professor Orton to be, for 

Glass-furnaces 10000000 cubic feet. 

Iron mills iooooooo " " 

Other factories 6000000 " " 

Domestic use 4000000 " " 

Total per day 30000000 " " 

In Indiana, large wells have been opened and used as in 
Ohio. In Pennsylvania, several of the large rolling-mills and 
glass-houses near Pittsburg were formerly supplied with mill- 
ions of feet per day ; but the supply, used so lavishly, became 
exhausted. In Canada, at Fort Erie and Windsor are wells, 
the gas from which is piped across the river to Buffalo and 
Detroit respectively. All through the oil regions gas wells 
are to be found more or less, accompanying every well sunk. 

From the composition of the gas, it will readily be seen 
that it is a valuable source of heat, the calorific power reach- 
ing 10000 calories or 1 100 B. T. U. per cubic foot. It is used 
for domestic purposes, steam, glass making, iron mills, brick 
burning, and numerous other ways, and until recently used 
wastefully in all. 



GASEOUS FUELS. IO/ 

As compared with coal, 57.25 pounds of coal or 63 pounds 
of coke are about equal to 1000 cubic feet of the gas. The 
actual equivalent in steaming or furnace work varies with the 
furnace, and probably with the people using it. Equivalent 
values of 14000 to 25000 cubic feet per ton of coal are 
reported, and hardly any two users will give the same yield. 
It seems to be especially adapted to glass-making, giving a 
long, clean, ashless, smokeless flame, and hundreds of glass- 
pots were set up in the neighborhood of the wells, especially 
in Ohio. Each pot consumes from 58000 to 61000 cubic feet 
per 24 hours in window-glass works and from 31000 to 49000 
cubic feet in flint-glass works, the difference being of 
course due to difference in burners and men, the gas being 
the same. 

In all cases where this gas is used the chief claim made, in 
addition to those of gases generally, has been cheapness, and 
it has been sold without any regard to its actual value. A 
comparison of its value with that of other gases is given by 
McMillin in the Report of the Ohio Geological Survey, vol. 
VI, page 544, as follows: 

1000 feet natural gas will evaporate 893 pounds of water. 



< i 


t i 


coal " " 


i i 


591 


i i 


i i 


water " " 


1 « 


262 


i I 


I i 


producer gas " 


< < 
OIL GAS. 


115 



There are several processes for producing gas from oil, 
usually petroleum or its derivatives. Some of them decom- 
pose the oil by means of heat alone, while others use steam, 
or steam and air together. The most successful pure oil 
process is the Pintsch ; this is used extensively in the large 
cities of Europe and America to obtain a gas for illuminating 
cars on railways. The gas is made by allowing the oil to fall 
drop by drop on a strongly heated surface. Complete decom- 



108 CALORIFIC POWER OF FUELS. 

position occurs, and a gas of high candle-power is formed. 
This is collected, and after compression supplied to the con- 
sumers. It loses some 20 per cent of the illuminating power 
during compression. As a source of heat, its use is, so far, 
very limited. An analysis and heat test will be found in the 
tables. 

The Archer gas process is somewhat similar to the Pintsch, 
but the products of decomposition are generated at a com- 
paratively low temperature, and then superheated subse- 
quently so as to make the gas permanent. This gas is used 
for metallurgical purposes, but its use for heating boilers is 
very limited. 

The other gases made with steam or steam and air have 
been advertised or pushed as fuel gases for several years. 
Many plants have been established and failed. A few of the 
most prominent are mentioned in the tables. 

OTHER GASES. 

Gas has been obtained from destructive distillation of 
wood, rosin, fats, and other materials. They were used prin- 
cipally for illumination, and seldom if ever for heat. They 
are now made only in very exceptional cases. 



CHAPTER X. 

CALORIFIC POWER OF COAL BURNT UNDER 
A STEAM-BOILER. 

FUEL USED AND WATER EVAPORATED. 
DISTRIBUTION OF THE HEAT PRODUCED. 

Experiments in heating steam-boilers have to deter- 
mine : 

1. How much water is vaporized by a given quantity of 
coal, so as to compare it with other coals or fuels ; 

2. The evaporative power of the steam-boiler used; 

3. A comparison of the various styles of grates or meth- 
ods of heating applied to steam-boilers. 

In this book we will consider only the first case, the 
others being outside of its scope. 

The knowledge of the heat of combustion of coal and 
other fuels is closely connected with experiments in heating 
steam-boilers. It is not enough to know the proportion of 
water which the apparatus or the fuel tested will vaporize : 
we must also determine the number of calories lost. We 
must know, besides, the composition of the coal and its heat 
of combustion, to determine the proportion of calories used to 
that possible with perfect combustion. 

The first work in this direction worth mentioning was 
probably that done by Peclet in 1833, but his results were 
very crude, and are of no account now. The next were those 
made by Prof. Johnson, in 1842 and 1843, for the U. S. 
Navy Department, to determine the steaming powers of the 

109 



HO CALORIFIC POWER OF FUELS. 

coals then in use. He analyzed and tested some thirty-five 
different coals, domestic and foreign. The tests were made 
with a specially built boiler, and careful and copious notes 
were taken all through. The chimney gases were analyzed, 
and an attempt made to determine their quantity. In 1891 
Mr. W. Kent* reviewed his work, and found that, with correc- 
tions for the constants employed by Johnson, the tests were 
comparable with those made at the present time. The 
figures given in the tables as Johnson's are with Kent's 
corrections. 

The first experiments based on the knowledge of the 
composition and heat of combustion of coal were published 
in 1868 and 1869 in the Bulletin de la Societe Industrielle 
de Mulhouse. Scheurer-Kestner remarks in the first part of 
this work, which he prosecuted later on with assistance of 
Meunier-Dollfus (Joe. cit. p. 1): 

"It is necessary to analyze the great difference found 
between the theoretical heat of combustion (at that time 
no actual determinations had been made) and the practical 
yield. 

" Several elements of the calculation aid in making this 
shortage. The principal ones are : 

" The heat of combustion of the coal; 

" The composition of the coal; 

" The composition of the cinders as drawn from the 
ash-pit ; 

' ' The quantity of water vaporized and the temperature 
of the steam produced ; 

"The volume of gases introduced under the grate, and 
their temperature when they leave the boiler to pass into the 
chimney ; 

"The composition of the gaseous products of combus- 
tion ; 

* Engineering and Mining Journal, Oct. 1891. 



WEIGHT OF FUEL. 1 1 1 

"The temperature of the cinders at the time of dumping; 

" The loss of caloric by radiation from the setting of the 
boiler." 

We must refer to mineral and organic as well as gas 
analysis to obtain the necessary elements for the distribution 
of the caloric produced by the combustion of the coal on a 
steam-boiler grate. 

To avoid referring to them, we will consider the composi- 
tion and heat of combustion of coal as known. (See tables.) 

WEIGHT OF FUEL. 

The coal used in the test should be kept under cover 
away from moisture and heat, so that the hygroscopic water 
it contains shall vary as little as possible from the time of 
taking the sample. Weigh the coal in the gross, and then 
weigh portions of about ioo kilograms (220 lbs.) on a scale 
sensible to 1 1 . 

Where practicable, a box open at the top and holding 
500 pounds of coal should be provided for each 25 square 
feet grate area, and in proportion for larger grates. It 
should be placed on the scales, and conveniently located for 
shoveling into the fire. 

The exact time of weighing should be noted and the 
exact weight set down. The weight should be taken at the 
instant of closing the fire-door. The box should be com- 
pletely emptied each time. The difference of weight at each 
firing will give the several quantities fired ; the differences of 
time will give the intervals between firing; and the differ- 
ence of time between successive charges will serve as a check 
on the record c e the test. A chart or diagram should be 
made showing the regularity of the working, and it is well to 
keep the records in tabular form ; weights in one column, time 
in another. 



112 CALORIFIC POWER OF FUELS. 



SAMPLING THE COAL. 



In all experiments for determining heat of combustion of 
fuels, the sampling must be done with the utmost care, espe- 
cially if the laboratory and working test are to be made at 
the same time. Samples accurately representing the coal of 
the working test must be kept in the laboratory, and when 
coal is tested which contains foreign matter and considerable 
moisture, too much care cannot be taken to prevent errors. 

The official method of the American Society of Mechanical 
Engineers is given in the Appendix, and answers the purpose 
very well. If very large quantities are to be sampled, remove 
a portion from each cart-load and then re-sample these as per 
directions above mentioned. 

It is not always necessary to resort to these methods. 
When the coal comes from the same pit and level, experience 
has shown that a piece which seems to agree with the general 
character is usually sufficient. Care must be taken to avoid 
samples having too much hanging-wall or bed-rock. For 
twenty years the pure coal of Ronchamp taken from the 
same pit has given the same calorimetric test, when it con- 
tained from 10 to 20 per cent of ash. Lord and Haas* 
showed that the same was true of many American mines, 
especially in Ohio and Pennsylvania. This being true, we 
could consider that in sampling we did not sample the coal, 
but the impurities; and that a sample showing the average 
impurities would give all that was needed, as we would know 
what the coal was. 

Care must be taken with regard to the moisture, and any 
coal showing much external moisture must be examined as 
near as possible to the original condition. For example, a 
coal containing 10 per cent of moisture in the pile may, after 
sampling, crushing< and resampling, lose all but 4 or 5 per 
cent. If the moisture was determined in this coal while in as 

* Trans. Am. Inst. Min. Eng., Feb. 1897. 



ANALYSIS OF COAL. 1 13 

large pieces as possible, this moisture would all be accounted 
for. 

In spite of all precautions, samples do not always agree in 
mineral content with the mass. The difference seems to be due 
not only to the unequal distribution of the foreign mineral 
matter throughout the coal, but principally to the difference 
in specific gravity between the coal and this mineral, so that 
the purer the coal the more satisfactory the sampling. 

Sometimes a coal is rich in foreign matter, and is contained 
in a tube open at one end. From this samples may be drawn 
showing differences of several per cents; as for example, 12.49 
and 16.74 per cent obtained in two successive cases. The 
following experiment shows how this happens and how to 
prevent it : 30 grams of coal, finely pulverized, and contain- 
ing 20 per cent of mineral, was put into a glass tube, which 
was closed with a cork and placed vertically, giving it slight 
taps to settle it down. In a short time most of the foreign 
material was at the bottom of the tube, the upper portion 
being nearly free. To avoid such an error the sample must 
be drawn only after thorough mixing, and without any shaking 
or jarring of the tube. It is well to use pastilles made up 
immediately after thorough mixing. A sample containing 
only 13 to 14 per cent of foreign matter has given from a 
tube, 12.20, 12.81, 13.12, 13.50, 14.42 per cent. 



ANALYSIS OF THE COAL. 

No attempt will be made to treat the methods of ana- 
lyzing coal ; still, as this usually accompanies a calorimetric 
determination, some hints may be useful. Scheurer-Kestner 
usually burns the coal in tubes of white glass placed on an 
iron gutter. The same tube may thus serve several times if 
asbestos cloth be placed between the tube and the iron and 
the cooling be properly regulated. His tubes are 70 to 75 
centimetres (27 to 29 inches) long and 15 to 20 millimetres 



114 CALORIFIC POWER OF FUELS. 

(0.6 to 0.8 inch) inside diameter. They are filled with copper 
oxide in small pieces, except at the front end, which has a 
small piece of metallic copper, and at the back, where the 
platinum boat containing the coal is placed. Usually half a 
gram is used for a test, the coal having been previously dried 
at ioo° to 105 C. (212° to 221° F.). 

Before putting in the sample the tube is heated to redness 
and thoroughly dried by means of a current of dry oxygen. 
The combustion is carried on so as to allow time enough for 
all the gas to be absorbed by the potash, during the first half 
of the time the bubbles passing through very slowly. There 
is no risk then of unburnt gases passing off. An iron or a 
platinum tube may be used in place of the glass one, but glass 
allows inspection at all times. 

An analysis should show the carbon, hydrogen, oxygen, 
nitrogen, sulphur, ash, and moisture, and they should be so 
given that the carbon, hydrogen, oxygen, nitrogen, sulphur, 
and ash should equal ioo per cent, the moisture being 
determined separately, or if preferred all but ash and moisture 
may foot up ioo, and those two be given separately. This 
latter method is the one which is followed by many of the 
European engineers, and will be found so in the tables given 
at the end of this book. If possible the approximate analysis 
should also be given. 

In determining the moisture too much care cannot be 
taken to expel all of it. With many coals, and especially our 
Western ones, the ordinary heating to no° C. is not suffi- 
cient. Kent, Carpenter, Hale, and others have investigated 
this question, and find that a much higher temperature is 
needed, and must be employed. In some cases as high as 
140 to 150 C. may be used with safety, and such tempera- 
tures are recommended by Carpenter, no appreciable amount 
of volatile matter being driven off. 



DURATION OF THE TEST. 



115 



ANALYSIS OF THE CINDERS. 

The cinders and ashes produced by the combustion of the 
coal are collected so as to weigh and sample them. After 
drying and determining the water the sample is put into a 
glass tube as with coal. As the quantity of hydrogen is 
usually very small, it need not be determined, and the 
calcination for the carbon can be performed in the open air. 
The following table contains the results of the tests made 
oy Scheurer-Kestner and Meunier-Dollfus on steam-boiler 
cinders : 



Carbon. . . 
Hydrogen 
Ash 



1 


2 


3 


9.20 

0.37 
89-95 


12.65 

O.29 

86.50 


6-73 

0.21 

92.64 


99-52 


99-44 


99.58 



8.92 

0.27 

91.42 



99.61 



The proportion of carbon in cinders may be as low as 7 
per cent, but is usually higher, and 10 to 12 per cent may be 
called good practice. 



DURATION OF THE TEST. 

A test should continue at least a whole day on account of 
certain irregularities and causes of error which are constant. 
The level of the water should be the same at the end of the 
test as at the beginning, since a slight difference in level 
means considerable water. 

The condition of the combustion at the time of stopping 
cannot always be ascertained, and this produces a cause of 
uncertainty. Another cause is from the temperature of the 
water in the boiler, and especially in the economizer. On 
short runs these sources of error cause very faulty results. 



Il6 CALORIFIC POWER OF FUELS. 



THE WATER EVAPORATED. 



The feed-water is preferably held in a gauged reservoir, or 
else weighed, meters not being certain unless checked fre- 
quently. Use only cold water or water whose temperature 
will vary but little during the test, so as to avoid corrections 
of temperature and expansion. The temperature usually 
varies so little that no account of this variation need be taken. 
Pump to the boiler with as much regularity as possible, and 
keep accurate record. 

To have the same level at the end as at the beginning, 
keep up the initial pressure and feed very carefully. The 
mean temperature of the feed-water is referred to o° C, con- 
sidering that the specific heat is constant. Otherwise we may 
use Regnault's formula, 

Q == t — 0.00002* 2 -f- 0.0000003*'. 

But when the temperature of the water varies no more than 
10 degrees, no appreciable error will be made by calling / 
equal to the temperature. 

TEMPERATURE OF THE STEAM. 

We may measure the temperature of the steam directly by 
a thermometer in the boiler, or indirectly by observing the 
pressure. Both methods should be used. . 

To take the temperature directly, the thermometer is 
placed in an iron tube closed at one end and reaching to the 
middle of the boiler. The tube should be filled with paraffin 
or some analogous substance. The temperature of the 
steam or the water may be taken as desired by changing the 
position of the thermometer in the tube. See Figure 39. 
Vertical maximum and minimum thermometers are very use- 
ful, preventing too hasty observations. 



MOISTURE IN THE STEAM. 1 17 

To measure the temperature by pressure an air-thermom- 
eter is used. A registering manometer aids the work consid- 
erably, as observations should be taken regularly at frequent 
and equal intervals. The temperature is calculated by means 
of tables of vapor-tension.* 

MOISTURE IN THE STEAM. 

The percentage of moisture should be ascertained by 
means of a throttling or a separating calorimeter, directions 
for the use of which will be furnished by the makers. They 
should easily and completely separate the water in a manner 
convenient for measuring, or better, for weighing. It is ad- 
visable to use two or three at the same time, thus serving as 
checks for each other. 

11 The throttling steam-calorimeter was first described by 
Professor Peabody in the Transactions, f vol. X. page 327, 
and its modifications by Mr. Barrus, vol. XI. page 790; vol. 
XVII. page 617; and by Professor Carpenter, vol. XII. page 
840 ; also the separating-calorimeter designed by Professor 
Carpenter, vol. XVII. page 608. These instruments are used 
to determine the moisture existing in a small sample of steam 
taken from the steam-pipe, and give results, when properly 
handled, which may be accepted as accurate within 0.5 per 
cent (this percentage being computed on the total quantity of 
the steam) for the sample taken. The possible error of 0.5 
per cent is the aggregate of the probable error of careful ob- 
servation, and of the errors due to inaccuracy of the pressure- 
gauges and thermometers ; to radiation ; and, in the case of 
the throttling-calorimeter, to the possible inaccuracy of the 
figure 0.48 for the specific heat of superheated steam, which 

* For full details regarding setting up an open-air manometer, see paper 
\)y Scheurer-Kestner and Meunier-Dollfus in the Bulletin de la Socie'te' in- 
dustriellc de Mulhouse, 1869, page 241; also Trans. A. S. M. £., vol. VI. 
pages 281 and 282. 

f Transactions A. S. M. E. 



Il8 CALORIFIC POWER OF FUELS. 

is used in computing the results. It is, however, by no means 
certain that the sample represents the average quality of the 
steam in the pipe from which the sample is taken. The prac- 
tical impossibility of obtaining an accurate sample, especially 
when the percentage of moisture exceeds two or three per 
cent, is shown in the two papers by Professor Jacobus in 
Transactions ,* vol. XVI. pages 448, 1017. 

" In trials of the ordinary forms of horizontal shell and of 
water-tube boilers, in which there is a large disengaging sur- 
face, when the water-level is carried at least 10 inches below 
the level of the steam outlet, and when the water is not of a 
character to cause foaming, and when in the case of water- 
tube boilers the steam outlet is placed in the rear of the mid- 
dle of the length of the water-drum, the maximum quantity 
of moisture in the steam rarely, if ever, exceeds two per cent ; 
and in such cases a sample taken with the precautions speci- 
fied in article XIII. of the Code may be considered to be an 
accurate average sample of the steam furnished by the boiler, 
and its percentage of moisture as determined by the throttling 
or separating calorimeter maybe considered as accurate within 
one half of one per cent. For scientific research, and in all 
cases in which there is reason to suspect that the moisture 
may exceed two per cent, a steam-separator should be placed 
in the steam-pipe, as near to the steam outlet of the boiler as 
convenient, well covered with felting, all the steam made by 
the boiler passing through it, and all the moisture caught by 
it carefully weighed after being cooled. A convenient method 
of obtaining the weight of the drip from the separator is to 
discharge it through a trap into a barrel of cold water stand- 
ing on a platform scale. A throttling or a separating calo- 
rimeter should be placed in the steam-pipe, just beyond the 
steam-separator, for the purpose of determining, by the 
sampling method, the small percentage of moisture which 
may still be in the steam after passing through the separator. 

* Transactions A. S. M. E. 



QUALITY OF STEAM. 1 19 

" The formula for calculating the percentage of moisture 
when the throttling-calorimeter is used is the following: 

H- h- k{T-t) 
w = 100 X ~l , 

in which w = percentage of moisture in the steam, H — total 
heat and L = latent heat per pound of steam at the pressure in 
the steam-pipe, h = total heat per pound of steam at the pres- 
sure in the discharge side of the calorimeter, k = specific heat 
of superheated steam, T= temperature of the throttled and 
superheated steam in the calorimeter, and t = temperature 
due to the pressure in the discharge side of the calorimeter, = 
212 Fahr. at atmospheric pressure. Taking £ = 0.48 and 
t = 212, the formula reduces to 

H— 1146.6- 0.48(7- 212)* „ 
w = 100 X 7 • 



CORRECTIONS FOR QUALITY OF STEAM. f 

Given the percentage of moisture or number of degrees of 
superheating, it is desirable to develop formulae showing what 
we have termed ' ' the factor of correction for quality of steam, " 
or the factor by which the " apparent evaporation," determined 
by a boiler-test, is to be multiplied to obtain the " evaporation 
corrected for quality of steam." It has been customary to call 
the proportional weight of steam in a mixture of steam and 
water "the quality of the steam," and it is not desirable to 
change this designation. The same term applies when the 
steam is superheated by employing the "equivalent evapora- 
tion," or that obtained by adding to the actual evaporation the 

* William Kent in the Report of the Committee on Boiler-tests, A. S. 
M. E. , 1897. 

f C. E. Emery in the Report of Committee on Boiler-tests, A. S. M. E., 
1897. 



120 CALORIFIC POWER OF FUELS. 

proportional weight of water which the thermal value of the 
superheating would evaporate into dry steam from and at the 
temperature due to the pressure. "The factor of correction 
for quality of steam " in a boiler-test differs from the ' ' quality " 
itself, from the fact that the temperature of the feed-water 
is lower than that of the steam. 
Let 

Q = quality of moist steam as described above; 
Q x = the quality of superheated steam as described above ; 
P= the proportion of moisture in the steam; 
k = the number of degrees of superheating; 
F= the factor of correction for the quality of the steam 

when the steam is moist ■ 
F x = the factor of correction for the quality of the steam 

when the steam is superheated ; 
H =. the total heat of the steam due to the steam-pressure; 
L = the latent heat of the steam due to the steam-pressure ; 
T = the temperature of the steam due to the steam-pressure ; 
T x = the total heat in the water at the temperature due to 

the steam-pressure;* 
J = the temperature of the feed- water; 
J x =z the total heat in the feed-water due to the temperature.* 

Therefore, for moist steam, 

Q = x-P, (i) 

P=i-Q, (2) 

Q + P=i (3) 

See also equation (6). 

* Most tables of the properties of steam and of water are based on the 
total heat of steam' and water above 32 degrees Fahr. For such tables the 
total heat in the water at a given temperature is equal approximately to 
the corresponding temperature minus 32 degrees. Exact values should, 
however, be taken from the tables. 



< 



QUALITY OF STEAM. 121 

With both the condensing and throttling calorimeters the 
water and steam are withdrawn from the boiler at the temper- 
ature of the steam, and with a separator the water can only be 
accurately measured when under pressure, so that the difference 
between the steam and the moisture in the steam, as they leave 
the boiler, is simply that the former has received the latent 
heat due to the pressure, and the latter has not. There is, 
however, imparted to the water in the boiler not only the 
latent heat in the portion evaporated, but the sensible heat 
due to raising the temperature of all the water from that of 
the feed -water to that of the steam due to the pressure. 

In equation (3) the proportional part Q receives from the 
boiler both the sensible and the latent heat, or the total heat 
above the temperature of the feed = Q{H — J x ) thermal units, 
and the part Pthe difference in sensible heat between the tem- 
peratures of the steam and of the feed-water ~ P(T 1 — ./,) 
thermal units. If all the water were evaporated, each pound 
would receive the total heat in the steam above the tempera- 
ture of the feed, or H — J x . (t The factor of correction for 
the quality of the steam," when there is no superheating, is 
therefore 



H-J, 



= Q + P\ 



$&)■■ • « 



The superheating of the steam requires 0.48 of a thermal 
unit for each degree the temperature of the steam is raised, 
so for k degrees of superheating there will be 0.48^ thermal 
units per pound weight of steam, and the " factor of correc- 
tion for the quality of the steam " with superheating. 

F '= h-L — = I + i/Z7- ' • (5) 

See also equation (7). 



122 CALORIFIC POWER OF FUELS. 

With the throttling-calorimeter the percentage of moisture 
P, or number of degrees of superheating, are determined as 
explained before. 

Since the invention of the throttling-calorimeter the use 
of the original condensing, or so-ealled barrel, calorimeter is 
no longer warranted. Accurate results should, however, be 
obtained by condensing all the steam generated in the boiler, 
and this plan has been followed in certain cases. It has,, 
therefore, been thought desirable to add other formulae ap- 
plicable to condensing-calorimeters. The following additional 
notation is required -. 

W = the original weight of the water in calorimeter, or 
weight of circulating water for a surface condenser. 

w = the weight of water added to the calorimeter by blow- 
ing steam into the water, or of " water of condensation " with 
a surface condenser. 

t = total heat of water corresponding to initial tempera- 
ture of water in calorimeter. 

t 1 = total heat of water corresponding to final temperature 
in calorimeter. 

Evidently, then : 

W{t x — i) = the total thermal units withdrawn from the 
boiler and imparted to the water in calorimeter. 

W 

— (/, — t) = the thermal units per pound of water with- 

w 

drawn from the boiler and imparted to the water in calorim- 
eter, from which should be deducted T i — t 1 to obtain the 
number of thermal units per pound of water withdrawn from 
the boiler at the pressure due to the temperature T. 

Since only the latent heat L is imparted to the portion of 
the water evaporated, the quality Q, or proportional quantity 
evaporated, may be obtained by dividing the total thermal 
units per pound of water abstracted at the pressure due to the 
temperature T by the latent heat L. Hence, as given in 



QUALITY OF SUPERHEATED STEAM. 123 



Appendix XVII., 1885 Code, with some differences in nota 
tion, 

w 



Q and Si — 7 



W 

-{t x -t)-{T x -Q 



(6) 



The value Q applies when the second term is less than 
unity. P may be derived therefrom by substitution in equa- 
tion (2) and F from equation (4). 

Q i applies when the second term of the above equation is 
greater than unity, which shows that the steam is superheated, 
and, as in this case, the heating value of the superheat has 
already been measured by heating the water of the calorim- 
eter; the proportional thermal value of the same, in terms 
of the latent heat Z, is represented directly by Q l — 1, and 
we have as the factor of correction for the quality of the steam 
with superheating, 

ff-S,+L(Q,-i) L(Q, - i ) 

F ' ~ ^^7 ~ + ~TT=J, ■ ■ (7) 

See also equation (5). 

When the quality is greater than 1, or equals Q 1 , the num- 
ber of degrees of superheating, 

k= L( itf L) - 2-o8 3 3£(& - I)- • • (8) 

THE QUALITY OF SUPERHEATED STEAM.* 

The quality of the superheated steam is determined from 
the number of degrees of superheating by using the following 
formula : 

Z + o-48(^-*) 
^~ L 

* G. H. Barrus in Report of Committee on Boiler-tests, A. S. M. E., 
1897. 



124 CALORIFIC POWER OF FUELS. 

in which L is the latent heat in British thermal units in one 
pound of steam of the observed pressure ; T the observed 
temperature, and / the normal temperature due to the pres- 
sure. This normal temperature should be determined by ob- 
taining a reading of the thermometer when the fires are in a 
dead condition and the superheat has disappeared. This tem- 
perature being observed when the pressure as shown by the 
gauge is the average of the readings taken during the trial, 
observations being made by the same instrument, errors of 
gauge or thermometer are practically eliminated. 



CHAPTER XI. 

AIR SUPPLIED AND GASEOUS PRODUCTS OF COM- 
BUSTION. 

VOLUME OF AIR NECESSARY TO COMBUSTION. 

Four elements are to be considered in calculating the 
theoretical volume of air for combustion : carbon, hydrogen, 
oxygen, sulphur. The last is sometimes wanting in coal, but 
not usually. 

Carbon. — The atomic weights of carbon and oxygen are 
as 12 and 16, and 2 atoms of oxygen are needed to form car- 
bonic acid with I atom of carbon. Then 

12 : 32 = i : 2.666. 

1 kilogram of oxygen occupies 0.699 cubic metre (Table IV); 
1 kilogram of carbon needs 

0.699 X 2.666 = 1.863 cubic metres of oxygen. 

Hydrogen. — The atomic weights of hydrogen and oxygen 
being respectively 1 and 16, and water being formed of 2 
atoms of hydrogen and 1 of oxygen, we have 

2 : 16= 1 : 8; 

and as 1 kilogram of oxygen occupies 0.699 cubic metre, I 
kilogram of hydrogen requires 

8 X 0.699 = 5.592 cubic metres of oxygen. 

125 



126 CALORIFIC POWER OF FUELS. 

Sulphur. — The atomic weights of sulphur and oxygen 
being as 32 to 16, and sulphurous acid containing 1 atom of 
sulphur and 2 atoms of oxygen, we have 

32 : 32 = 1 : 1. 

1 kilogram of oxygen occupies 0.699 cubic metre; 1 kilo- 
gram of sulphur needs, then, to form sulphurous acid 

1 X 0.699 — 0.699 cubic metre of oxygen. 

As most fuels have some oxygen in their composition, we 
must deduct this at the rate of 0.699 cubic metre per kilo- 
gram. 

Then multiplying these results by 4.77 (Table XIV) we 
obtain the number of cubic metres of air required. 

A similar method of calculation will give 

For one pound of carbon 29.86 cubic feet of oxygen. 

" hydrogen 89.60 " " " 

" " " " sulphur 11.20 " " " 

As an example, take a coal containing 90$ C, 5$ H, 3.5$ 
O, o.ifo N, and 0.5$ S. 

C 0.900 X 1.863 = 1.677 cubic metres. 

H 0.040X5.592=0.224 

S 0.005 X 0.699 — °-003 

Total oxygen 1 .904 

O . . . .0.035 X 0.699 = 0.024 

1.880 

1.880 X 4.77 = 8.967 cubic metres of air per kilogram of 
coal; or 143.98 cubic feet of air to the pound of coal. 

This result of course is only approximate, as complete 
combustion is not attained with coal and solid fuels. With 
liquid fuels, and especially gases, however, the combustion is 
usually complete. 



VOLUME OF WASTE GASES BY ANALYSIS. 127 

Tables V and VI gives the coefficients to be employed in 
the calculations. 

Table XIII gives the theoretical quantity of air required 
for the combustion of various fuels; the actual quantity 
used depends on the conditions of firing, fuel, etc, and is 
seldom less than twice the amount shown in the table, except 
perhaps with gases. 

VOLUME OF WASTE GASES BY ANALYSIS. 

For a long time efforts have been made to determine the 
quantity of air used by comparison of the analyses of the 
waste gases with those of the fuel used. Many analyses 
have been published, but the results showed so little regu- 
larity, and were so contradictory even, that it was impossible 
to form any conclusion further than that waste gases from 
coal may contain at the same time both combustible gas and 
an excess of air. 

Peclet, in 1827, published the first analyses, made with 
samples collected from a boiler-stack by means of an inverted 
flask containing water. Ebelmen, in 1844, published a 
memoir on the composition of gases from industrial furnaces. 
He analyzed the gases from a metallurgical furnace, the gas 
being collected by an aspirator. In 1847 Combes made a 
report on methods of burning or preventing smoke, giving 
analyses by Debette. In these the first attempts were made 
to obtain average samples, they being drawn at certain deter- 
mined stages of the heat and the fuel. 

In 1862 Commines de Marcilly published analyses of 
gases from locomotives, as well as from stationary boilers, 
but the author said the time of collection lasted only a few 
seconds. In 1866 Cailletet showed that, to obtain correct 
results, the gas should not be collected till somewhat cooled ; 
otherwise, on account of dissociation, a larger proportion of 
combustible gas is found than when cooler. 

But, on account of the defective methods of sampling 



128 CALORIFIC POWER OF FUELS. 

used, no conclusion other than that stated above can be 
drawn from these analyses, and no possible idea can be 
deduced as to the actual composition of the gases as a whole. 
When we try to use laboratory methods of control in practi- 
cal workings, the first necessity is to obtain correct samples 
for analysis, that is, average samples. In this respect all the 
above -quoted authors are deficient. The tests made by 
Scheurer-Kestner, published in 1868, were the first to con- 
form to this requirement. His samples were drawn by a 
system analogous in principle to that described for sampling 
coal. 

It is not always necessary to resort to such a complicated 
operation in case of a permanent gas; samples taken from 
the general current by means of an ordinary aspirator or an 
oil-aspirator (page 132) will usually do if drawn at a sufficient 
distance from the fire. If the gases have passed through a 
long flue, especially one with several bends, they are suffi- 
ciently mixed, and may be considered as a homogeneous gas. 
We must remember, however, that as we recede from the 
fire the infiltration of air, if not prevented, becomes greater. 
In careful experiments, the method to be described of frac- 
tionating a large volume is preferable. 

GAS SAMPLER. 

In principle the apparatus consists of a falling-water 
aspirator, and a second mercury aspirator drawing a small 
fraction of the gases from the current of the first in a con- 
stant regular manner and keeping it in a mercury gas-holder, 
A (Fig. 28), which is a strong glass flask of 3 litres capacity, 
holding about 40 kilograms (88 lbs.) of mercury. The 
gas-holder is connected by the tube a with the tube c for 
sampling the gas, the flask A and its accessories acting as 
a Mariotte flask. , It is closed at the top by a stopper 
hollowed out conically below and having holes for two 
tubes, a and b. This hollowing is to permit filling without 






GAS SAMPLER. 



129 



any air-bubbles. The tubes a and b have glass stop-cocks, 
but the one in a may be omitted. The manometric tube c 
shows the pressure. Tube d, like c, passes through a rubber 
stopper, closing the horizontal tubulature of the gas-holder. 




% 



*» 






Fig. 28. — Gas Sampler. 



Fig. 29. — Sampler Tube. 



This tube can be rotated in the stopper to the position shown, 
or to one 180 from such position. The flask is graduated on 
the side into millimetres. Tube a fits the hole of the stopper 
tightly, and can be moved up or down as desired to suit the 
quantity of gas in the flask. All joints are covered with 
paraffin, tube a being greased to facilitate movement. 

Fig. 29 shows the gas sampling tube. It consists of a 
platinum cylinder, rs, 10 millimetres (0.4 inch) diameter and 
700 millimetres (27.5 inches) long, having a longitudinal slot 
of several centimetres length. The end r is closed with a 



13° CALORIFIC POWER OF FUELS. 

platinum cap ; the end s is soldered to a copper tube, sy, pass- 
ing into a Liebig condenser having two tubes, oo' ', for the 
water. In most cases the platinum tube may be replaced 
without trouble by one of copper, or even iron, the platinum 
being necessary only when the gases are drawn at a tempera- 
perature high enough to cause oxidation of the other metals. 
With iron or copper a portion of the oxygen is removed in 
the passage through the tube. 

The tube ry is open at y, and has a side tube h. Aspira- 
tion is carried on through the opening in the platinum tube. 
A movable rod, ik f carrying a platinum scraper is attached 
to one end of the tube, and moves in the slot to clean it, as 
occasion requires, from soot, etc. The disk/) serves to hold the 
cement used in fastening it to the stack or chimney, and pre- 
vents ingress of external air. The rod mn passes through a 
caoutchouc bearing fastened between the disks/ and q. 

Fig. 28 represents a front view of the apparatus. Fig. 30 
represents a side view in elevation. The tube ry is intro- 
duced through an opening made for the purpose in the 
masonry, the part rs being exposed inside. The end y, is 
connected with a lead pipe, v, by a rubber tube; this pipe is 
soldered to another one, yz. On opening the cock y t water 
flows from a reservoir and empties at z. Suction in yrs 
should amount to several millimetres of mercury, and is regu- 
lated by the cocks y and x controlling the water-flow, and also 
by the length of yz. The gas drawn in by yvx may be meas- 
ured by collecting it at z, and should amount to 4 or 5 litres 
(25 to 30 cubic inches) per minute. 

The gas-holder is supported by a piece of sheet iron with 
upturned edges forming a shelf. Any mercury spattered 
over or spilled is thus easily collected. The mercury tank is 
supported from the wall of the chimney in such position as to 
facilitate refilling the flask through a siphon. The tubes dd r 
serve to feed the condenser. 

While the current is passing through yr a small quantity 



GAS SAMPLER. 



131 



is drawn out by the tube k, and this should be so regulated 
by the cock d that only from ^-J-^ to -g-J-g- is collected. 

Whenever the level of the mercury lowers, it shows a 




Fig. 30. — Gas Sampler. 

clogging in the slot, and it should be cleaned by moving the 
rod. This always indicates when cleaning is necessary, and 
it sometimes keeps clean for hours. 

When a sufficient sample has been obtained turn up the 
tube d, and then the gas-holder can be carried away. 

The method recommended by the American Society of 
Mechanical Engineers is to have a "box or block of gal- 
vanized sheet iron equal in thickness to one course of brick," 
and secure in it a series of J-inch gas-pipes, all alike at the 
ends and of equal lengths, in such manner that the open ends 
may be evenly distributed over the area of the flue A (Fig. 
32), and their other open ends enclosed in the receiver B. 



132 



CALORIFIC POWER OF FUELS. 




Fig. 31. — Oil Aspirator. 



If the flue-gases be drawn off from the receiver B by 
four tubes, CC, into a mixing-box, 
D, beneath, a good mixture can be 
obtained. Two such samplers, one 
above the other, a foot apart, in the 
same flue will furnish samples of 
gases which show the same compo- 
sition by analysis. 

The oil gas holder (Fig. 31) con- 
sists of a bottle tubulated at the 
bottom and connected with the sup- 
ply of gas at the upper opening. It 
may contain some 10 litres (600 
cubic inches), and is filled with 
water having on it a layer of 10 
centimetres (4 inches) of oil. The 
water running out from the tubu- 
lature at the bottom draws the gas 
in at the top. The stopper at the top has two openings, 
through one of which passes a funnel-tube, through which 
water may be poured to expel the gas when portions of it 
are needed. The gas then passes out by the same tube 
through which it was drawn into the bottle. 

With all kinds of aspirators or gas holders especial care 
must be taken to prevent entrance of air into the flue after 
leaving the fire, since the correct analysis will show not only 
the quantity of unburnt gases, but also the excess of air, and 
any mixture of outside air will vitiate the result and cause 
faulty deductions as to the working of the fire ; and conse- 
quently the waste calories. 

To prevent this, all joints in the masonry must be exam- 
ined and repaired if necessary. In case of dampers, which 
must be used, the bearings can be made in stuffing-boxes, as 
recommended by Burnet. Generally, the gas can be sampled 
before it arrives at a damper, as the course of the boiler-flue 



GAS SAMPLER. 



133 



is usually sufficient to cause a thorough mixing of the gases. 
In case there are several dampers, the first one may be dis- 
pensed with for the time being. 

When the gases are taken quite near the fire, they must be 
drawn very slowly in order to gradually cool them down and 





Fig. 32. 

avoid dissociation. In this case a stoneware tube may be 
used for suction. If this precaution is neglected the gases 
collected may be entirely different from those passing off at 
the chimney. Metal tubes are inadmissible, since they 
abstract oxygen, and hence cause a change in composition. 



ANALYSIS OF THE GASES. 



The collected gases contain nitrogen, oxygen, carbonic 
acid, carbonic oxide, hydrocarbons, and occasionally free 
hydrogen. To determine all these a eudiometric method 



134 



CALORIFIC POWER OF FUELS. 



must be used ; but usually only the oxygen, carbonic oxide, 
and carbonic acid are required. In normal combustion with 
sufficient air the quantity of hydrocarbons is very trifling, and 
need not be considered. This occurs usually with a supply 
of 15 cubic metres of air per kilogram (240 cubic feet per 
pound) of coal, and should produce a waste gas containing 10 
to 14 per cent of carbonic acid, in which case the unburnt 
hydrocarbons amount to less than 1 per cent. 

The Orsat apparatus or its modifications may be used to 
determine the oxygen, carbonic acid, and carbonic oxide. By 
using Winckler's modification the hydrocarbons may be deter- 
mined. For exact analyses of the gases the Hempel apparatus 
may be used. For general work, however, the Orsat appa- 
ratus or the Orsat-Muencke is the best and most easily 
transported and handled. Directions for using this apparatus 
need not be given here, as they can be found in all works on 
gas analysis, or can be had of the dealers. 

The following table gives analyses made by Scheurer- 
Kestner of waste gases from Ronchamp coal. The gases for 
examination were collected by means of the apparatus described 
above (pp. 128 et seq.) and shows the average for a whole 
day's run. 





Percentage Composition of the Gases. 


<u 

a 
X* 


U 


bjo 


en 




T3 




V 

•0 


Hydrocarbons. 


U 


1) 




< 











>» 


X 

.s 


c 

V 

ha 

u 


O 

O 
.O 
U 


a 

V 

bo 
>> 

X 


'5 



a 



J3 


O 

-a 
>> 


u u v 




*3 




c 

3 be 
crc 
oi- 


< 


£ 


U 


O 


U 


u 


X 


u 


£ 


fa 
















Lbs. 


Lbs. 




6.60 


80.38 


14.87 


1. 41 


O.84 


1. 15 


1-35 


8.19 


15-4 


< 


10.47 


80.60 


I4.16 


2.18 


O.97 


0.98 


1. 11 


9.625 


30.8 


8' 


13-32 


80.66 


I4.63 


2.8o 


O.86 


0.49 


0.56 


9-625 


15-4 


4' 


17.61 


81.52 


13-34 


3-77 


O.86 


0.46 


0.91 


8.19 


15.4 


3 


20.94 


80.23 


13-43 


4.42 


O.24 


0.32 


1. 41 


8.19 


30.8 


10' 


26.18 


80.34 


12.89- 


5-53 


O.24 


0.28 


0.96 


4.71 


15-4 


8' 


42.84 


79-76 


10.87 


8.99 


O.24 


0.19 


0.19 


18.94 


15.4 


2 


53.78 


79.86 


8.23 


n-35 


O.24 


04 


0.52 


3-41 


13.2 


10' 



GAS SAMPLED. 



135 



The following table gives some analyses by Bunte of gas 
samples from coal burnt in his experimental apparatus at 
Munich : 





Min. and 














Max. 


CO, 


CO 


H 


O 


N 




of Air. 












Coal from the Ruhr 




10.26 


0.53 
1.94 

0.48 

1.22 


O.OI 


IO.OO 


79.20 

78.64 
79.30 
79.28 
80.14 


Do. 




16.45 
13.40 
H-45 

8.15 


i-45 
0.30 
0.78 
0.01 


1.52 

6.52 

7.27 

II.60 


Do. 




Do. 




Do. (grate more open). 




0. IO 


Do. Do. 




6.12 


O.89 


O.IO 


14.21 


78.68 


Coal from Saarbruck: Koenig.. 


j Min. ' 
I Max. 


15.12 

7.07 


I.09 
O.I8 


1.02 
O.OO 


2.64 
12.57 


80.13 
80.25 


" " Tremosna: Bohemia 


( Min. 
| Max. 


13.78 


4.69 


O.16 


1. 10 


80.27 




7-94 


0.03 


O.O9 


11.03 


80.91 


" " Hausham: Bavaria. 


j Min. 
1 Max. 


10.48 


0.07 


O.ig 


9.28 


79.98 




5.71 


O.I4 


O.08 


14.86 


79.21 


" " Miesbach: Bavaria. 


j Min. 
( Max. 


11.46 


0.07 


O.07 


8.66 


79-74 




5 42 


O.O3 


0.02 


15.00 


79-53 


" '' Bohemia 


( Min. 
1 Max. 


17.48 
12.20 


I. 21 

? 


O.06 
O.3O 


3.13 

7.87 


7S.12 




? 


" " the Ruhr : General 


j Min. 
1 Max. 


16.45 


I.94 


1-45 


1.52 


78.64 


Erbstolln 


3 95 


O.06 


O.OO 


16.41 


79-58 


" '" the Ruhr : Gelsen- 


j Min. 
( Max. 
j Min. 
/ Max. 
j Min. 
1 Max. 


10.46 


O.I I 


O. II 


8.58 


80.74 


kirchen 


5-44 
10.73 


O.I2 


O. IO 


14-15 
7-36 


80.19 
81.46 


" " Saarbruck : Saint- 


O.I5 


O.3O 


Ingbert 


7.48 
I3-30 


0.07 
0.6l 


O. IO 


11. 91 
4-13 


80.44 
81.63 


" " Saarbruck : Mittel- 


0.33 


bexbach 


8.44 


O.I9 


O.I6 


10.58 


80.63 


" " Saarbruck : Heinitz 


j Min. 
( Max. 


14.62 
6.49 


2 07 
0.07 


I. OO 
O.06 


2.07 
12.70 


80.24 
80.68 


" " Saarbruck: mixed.. 


j Min. 
1 Max. 


10.22 


0.22 


0.07 


8.57 


80.92 




8.21 


O.O4 


0.02 


10.64 


81.09 


'' " Bohemia 


j Min. 
( Max. 


i5-5o 
8.48 


O.74 
O.08 


0-33 
0.07 


1.67 
9.69 


81.66 




81.68 


• < 


j Min. 
1 Max. 


9.61 
7.00 


O.I6 
O.I I 


O.08 
0.05 


9-47 

12.70 


80.68 




80.14 


" " Saxony...., 


j Min. 
1 Max. 


13.80 
7.60 


0.33 
O.I6 


O.3O 
O.O9 


4-36 
11-53 


81.21 




80.62 


" " Silesia 


j Min. 
"j Max. 


n. 4 

8.07 


O 15 
O.IO 


O.O4 

O.O9 


7-45 
10.73 


81.22 




81.01 


" " Bavaria : Peissen- 


] Min. 
} Max. 
j Min. 
"j Max. 


13.96 


1.46 


O.79 


2-93 


80.86 


berer 


7-85 

14.91 

6.36 


0.07 
1.04 
0.16 


013 
O.60 
O.23 


10.57 
2.92 

13-15 


81.38 

80.53 
80.10 


s * 

Lignite from Bohemia 


Coke from Saarbruck 


j Min. 
1 Max. 


14.87 
8.01 


0.13 
0.03 


O.O9 
O.OO 


4.16 
10.87 


80.75 




81.09 



The data in the above table show that when air to the 
amount of 15 cubic metres and over per kilogram (200 cubic 



l Z& CALORIFIC POWER OF FUELS. 

feet per pound) is used, corresponding to a maximum of 14 
per cent of carbonic acid in the waste gases, the loss in hydro- 
gen is very small. With 12 per cent of carbonic acid the 
hydrogen loss amounts to only a few thousandths. 

CALCULATION OF THE VOLUME FROM ANALYSIS. 

To calculate this volume, determine the weight of carbon 
in a unit of volume, and knowing the weight of carbon fur- 
nished by the coal, determine the volume corresponding to 
the unit of weight. The unit of volume for the gas is the 
cubic metre, and the unit of weight, the kilogram. 

Carbon exists in the waste gases as carbonic acid, carbonic 
oxide, and hydrocarbons; when we do not know the compo- 
sition of the hydrocarbons, we consider the carbon and hydro- 
gen as free, and that the carbon is in the state of vapor. 

To determine the weight of carbon contained in these 
different gases, reduce their volumes to kilograms, and by 
means of their molecular (or equivalent) weights and that of 
carbon make the calculation. 

1 litre of CO, at o° and 760 mm. weighs 1.966 grams. 
1 " " CO " " " " " " 1. 251 

1 " " C vapor " " " 1.072 

Molecular weight of carbon 12 

" C0 2 44 

" CO 28 

The weight of a volume v of carbonic acid is v X 1.966, 
and as 44 of carbonic acid contain 12 of carbon, then the 
weight of carbon would be as 44 : 12 or as 1 1 : 3. Then 

= 0.536^. 



CALCULATION OF THE VOLUME FROM ANALYSIS. l$7 

The weight of carbonic oxide of volume v is 1.25 1 2/, and 
as 28 of carbonic oxide contains 12 of carbon, the ratio be- 
comes 28 : 12 = 7:3. We then have 

v X 1.251 X 3 , , 
= 0.5362/. 

7 

The weight of a volume of carbon vapor is v" X 1.072. 

To calculate the weight of carbon in a cubic metre of gas r 
multiply the added volumes of CO a and CO by the coefficient 
O.536. Multiply the volume of carbon vapor by 1.072, and 
add this product to that obtained above. The sum is the 
weight of carbon per cubic metre, 

C = 0.536(2/ -f 2/) -f- 1.0722/'. 

If the gas contains, per cubic metre, 60 litres of carbonic 
acid, 10 of carbonic oxide, and 1 of carbon vapor, we will 
have 

c — 0.536(60 -f- 10) -f- 1.072 X 1 ~ 38-592 grams carbon. 

From the ratio of carbon of the coal consumed and that in 
the gas the volume of combustion gases is deduced. 

To calculate this, subtract the carbon of the cinders from 
that of the original coal. If the coal contains 81 percent 
carbon and leaves 6 percent of cinders containing 10 percent 
of carbon, then the amount of carbon burnt will be 

81 — (o. 10 X 6.0) = 81 — 0.6 = 80.4. 

We then have 

38.592 : IOOO = 804: 20.830 litres. 

A kilogram of coal produces, then, 20.83 cubic metres of gas 
at o° and 760 mm. 

The general formula is 

C-c 



V = 



(v + z/)o. 5 36 -f- 1 .0722/' ' 



138 CALORIFIC POWER OF FUELS, 

in which 

y = volume of waste gases at o° and 760 mm. in cubic metres; 
v = " " CO a in litres per cubic metre of gases; 
„j n a (~*C) lt li '< (l (i li il 

v"= il il carbon vapor per cubic metre of gases; 

C = weight of carbon in grams, contained in 1 kilogram of 

coal; 
c = weight of carbon in grams, contained in cinders from I 

kilogram of coal. 

Note. — The above calculation in English units would be as follows: 

Weight of 1 cubic foot of carbonic acid o. 12274 lb. 

" " 1 " " " " oxide 0.07811 " 

" " 1 " " " carbon vapor 0.06693 " 

v X 0.12274 X 3 

— = 0.03352/. 



11 

7/ X0.07811 X 3 



= 0.03352; 



7 

0.06693^" = weight of carbon in vapor. 
C — 0.0335(2/ -f- v') + 0.066937/". 

1000 cubic feet of gases having 60 cubic feet of CO a , 10 cubic feet of CO 
and 1 cubic foot of C vapor would give 

C = 0.0335(60 -f- 10) + 0.06693 X 1 = 2.412 lbs. carbon. 

1 pound of coal has 80.4 per cent carbon; then 

2.412 : 1000 = 0.804 : 333£ cubic feet of gases produced from 1 lb. of coal. 

The general formula is 

V= C -^± , 

0.0335(2/ + v ) + 0.066932/" 

in which 

V = volume in cubic feet of gases produced; 

v = " of C0 2 in cubic feet per 1000 cubic feet; 

v' = " " CO " " '* " 

v" = " " carbon vapor in cubic feet per 1000 cubic feet; 

C = weight of carbon in coal in thousandths of a pound; 

c = " " " " cinders per pound of coal in thousandths. 



CALCULATION OF VOLUME OF AIR SUPPLIED. 139 

CALCULATION OF VOLUME OF AIR SUPPLIED. 

The volume of combustion-gases just determined is less 
than that of the air supplied. Oxygen in forming carbonic 
acid produces a volume equal to itself; hence there is no 
change. 

c + a a = co a 

2 VOls. 2 VOls. 

Oxygen in forming carbonic oxide produces twice the 
volume. 

C + O = CO 

I VOl. 2 VOls. 

Hence there is an increase in volume. 

Carbon vapor and hydrogen as free gases or as hydro- 
carbons increase the volume but slightly. In forming sul- 
phurous acid with sulphur there is no change of volume. 

S + 2 = S0 2 

2 VOls. 2 VOls. 

Another slight cause of increase is setting free the nitrogen 
of the coal ; but this is inappreciable. I per cent of nitrogen 
forms only o.i per cent of the entire volume of gases formed. 

It might be said that, excepting the oxygen changing to 
water and disappearing by condensation, all the modifications 
of gaseous volume may be neglected, the increase being more 
than compensated by the loss due to oxygen. This elimina- 
tion of oxygen must be allowed for, however. 

A coal containing 4 per cent of hydrogen requires eight 
times such weight to form water, or 40 grams of hydrogen 
need 320 grams of oxygen. 1 litre of oxygen weighs 1.430 
grams, then 320 grams measure ^ftb ~ 22 3-7 litres (7-9 cubic 
feet). (Or 1 lb. of such coal would need 3.6 cubic feet of 
oxygen.) 

These 223 litres must be added to the volume of the 
waste gases produced by the coal to obtain the original 



140 CALORIFIC POWER OF FUELS. 

volume of air introduced. A coal containing 5 per cent of 
hydrogen would use 279 litres. 

The volume of oxygen needed for various percentages of 
hydrogen is as follows : 

Per kilo of coal. Per lb. of coal. 

ifo hydrogen uses of oxygen 55.9 litres, 0.9 cubic feet. 

2 " " " 112 " 1.8 

3 " " " 168 " 2.7 

4 " " " 223 " 3.6 

5 " " " 279 " 4.5 
Calling H the per cent of hydrogen, the formula given 

above becomes 

V/ ~ O + O0.563 + 1.07W" + 55 ' 9 H> 
or 

t C -c' 

V/ = 0.0335b +z/') + 0.06693*" + °' 9 H * 

To make this applicable to normal air saturated with 
moisture at o° C. and 760 mm. (32 F. and 29.922 inches) 
containing 0.4 per cent of CO a , we must divide by 99.12, 
the composition of air being: 

Nitrogen 78.35 

Oxygen 20. 77 

Water 0.84 



o. 
Carbonic acid , 0.04 



100.00 
And 100 — 0.88 = 99. 12. The formula then becomes 

Q-c' 

V,/ -( Z ;_|_ ^0.567+ i.o8o6z/" + 55 '9 H > 
or 

„_ C- c' 

V ' ~ 0.0337(2; + v') + 0.06752^ + °-9 H - 



CALCULATION OF WEIGHT OF WASTE GASES. I4I 

CALCULATION OF WEIGHT OF WASTE GASES FROM 
• ANALYSIS. * 

Two methods of calculating from the analysis by volume 
of the dry chimney gases the number of pounds of dry chim- 
ney gases per pound of carbon, or the weight of air supplied 
per pound of carbon, have been given by different writers. 
These may be expressed in the shape of formulae as follows: 

(A) Pounds dry gas per pound C = ; — — ! ; 

(B) Pounds air per pound C = 5-8— — -~^ '-— . 

Formula A may be derived from the method of computa- 
tion given in Mr. R. S. Hale's paper on "Flue Gas Anal- 
yses," Transactions A. S. M. E., vol. XVIII. p. 901, and 
formula B from the method given in Peabody and Miller's 
Treatise on Steam-boilers. Both are based on the principle 
that the density, relatively to hydrogen, of an elementary gas 
(O and N) is proportional to its atomic weight, and that of a 
compound gas (CO and C0 2 ) to one half its molecular weight. 
Both formulae are very nearly accurate when pure carbon is 
the fuel burned ; but formula B is inaccurate when the fuel 
contains hydrogen, for the reason that that portion of the 
oxygen of the air-supply which is required to burn the 
hydrogen is contained in the chimney gas as H a O, and does 
not appear in the analysis of the dry gas. 

The following calculations of a supposed case of combus- 
tion of hydrogenous fuel illustrates the accuracy of formula. A 
and the inaccuracy of formula B : Assume that the coal has 
the following analysis : C, 66.50; H, 4. 55; O, 8.40; N, 1.00; 
water, 10.00; ash and sulphur, 9.55; total, 100. Assume 

* William Kent in Report of Committee on Boiler-tests, A. S. M. E., 

1897. 



142 CALORIFIC POWER OF FUELS. 

also that one tenth of the C is burned to CO, and nine tenths 
to C0 2 ; that the air supply is 20 per cent in excess of that 
required for this combustion ; that the air contains one per 
cent by weight of moisture ; and that the S in the coal may 
be considered as part of the ash. We then have the follow- 
ing synthesis of results of the combustion of 100 pounds of 
coal: 



O from N = Total 

Air. O X 23. Air. 



CO a CO H a O 

59.85 lbs. C to CO a X 2f 159-60 534-31 693.91 219.45 

6.65 " C to CO X ii 8.87 29.70 38.57 15.52 

3.50 " H to H 2 X 8 28.00 93.74 121.74 3i-5o 



196.47 657.75 854-22 



1.05 


'« H to H 2 ) 

" H to H a O ) 


8.40 


10.00 


11 Water 


1. 00 


" N 


9.55 


" Ash and S 


100.00 




Excess 


of air 20 per cent. 



9-45 
10.00 



39.29 131.55 170.84 



1025.06 

Moisture in air 1 per cent 10.25 



Total wt. of gases, 1125.67 = 39.29 790.30 219.45 15.52 61.20 

Total dry gases, 1064.56 

O N CO a CO 

Total dry gases, by weight, % 3.69 74.24 20.61 1.546 

Total dry gases, by volume, % 3.508 80.656 14.252 1.584 



Total gases 1125.76 + ash and S 9.55 = 1135.31 total products. 

Total air 1025.06 + moisture in air 10.25 + coa\ 100 = 1135.31. 

Dry gas per pound coal 10.6456; per pound carbon = 10.6456 -f- 665 = 16.008. 

Dry air per pound coal 10.2506; per pound carbon = 10.2506 -f- 665 = 15.414. 

Computation of the weight of dry gas and of air per pound C: 

Formula A : 

_ . _ I4.252XII + 3-508X8 + 82.240X7 , e , 

Dry gas per pound C = — - — - ' — : = 16.008 pounds. 

3(14-252 + 1.584) 
Formula B : 

, ~- „ 2(14.252 + 3.508) + 1.584 

Air per pound C = 5-8 v , — ~ — — - — 13.589 pounds. 

14.252 + 1.584 

The error in the last result is 15.414 — 13.589 = 1.825 pounds. 



WASTE GASES BY THE ANEMOMETER. 143 

Prof. Jacobus recommends the use of the formula 

7N 
Pounds of air per pound C = , rn . rn , -f- 0.77 ; 

and in the case given above, where the actual quantity used 
was 15.414 per cent, his calculated one is 15.434 per cent, — 
practically the same, and as near as errors of analysis would 
allow a calculated result. 



VOLUME OF WASTE GASES BY THE ANEMOMETER. 

The fan-wheel anemometer is an instrument to measure 
the force or rapidity of a current of gas. It consists of a 
fan-wheel rotated by the moving gas, and which transmits 
such motion to an index showing the number of revolutions. 
Burnat used this apparatus to measure the quantity of air 
passing in under the grate of steam-boilers. 

The coefficient to be used in calculating the flow is differ- 
ent for each machine, and must be determined by actual 
experiment. Burnat's formula, 

v = o. 120 -\- o. 130/2, 

means that the velocity is found by multiplying the number 
of revolutions per second by 0.130 and adding 0.120 to the 
product. 

To obtain satisfactory results with the anemometer, it 
must be placed in the axis of a perfect cylinder at the depth 
of a metre, as the indications vary with the position in the 
flue. The formula needs correction for temperature, but the 
correction of the apparatus much exceeds this. Burnat com- 
pared his results with those obtained from a formula depend- 
ing on the depression if under the grate (see page 147), and 
found differences of not more than 5 per cent. 



144 



CALORIFIC POWER OF FUELS. 



FLETCHER'S ANEMOMETER. 

Fletcher's anemometer (Fig. 35) is used in England to 
ascertain the speed of flow in chimneys and flues. In its 
simplified form it is quite serviceable. It is based on the 
movement of a column of ether in a U-tube. 

The ends of the glass tubes a, b are placed in the flue a 
little less than one sixth of its diameter. The straight end a 





Fig. 33. — Fletcher's Anemometer. 



should be parallel to the direction of the current, the end b 
being at right angles to this. Hunter proposed bending 
both ends in opposite directions, to obviate the error caused 
if the tubes were not so placed. These tubes communicate 
with the ether tube cd. The draught across the tubes causes 
the ether to rise in a by aspiration and to fall in b by pres- 
sure. The difference of level is read, and then the tubes are 
turned around 180 , so as to reverse their positions, and the 
difference of level read again. The sum of the two differ- 
ences is called the anemometer reading, and by means of 
tables the velocity of the current is ascertained. 

The same trouble is common to all anemometer methods. 
The flue feeding the fire receives only the air passing in 



HIRN'S METHOD. 



145 



under the grate. Whatever passes in by the doors or 
through cracks escapes accounting. On account 
of this it is certain that the calculations based on 
anemometer readings are lower than th al 

air supply. 

segur's differential gauge. 
This gauge (Fig. 34) consists of a U-tubeof 
■J-inch glass, surmounted by two chambers of 2\ 
inches diameter. Two non-miscible liquids of 
different colors, usually alcohol and paraffin oil, 
are put into the two arms, one occupying the 
portion AB, the other the portion BCD. The 
movement of the line of demarcation is pro- 
portional to the difference in area of the chambers 
and the tube adjoining. A movement of 2 
inches in the column represents J-inch difference 
pressure or draft. 




Fig. 34. 
Segur Gauge. 






hirn's METHOD. 

The apparatus used by Burnat as a check on his own 
calculations was devised by Hirn, and is based on the formula 
of the rate of flow of compressed gases from a reservoir, 
friction being neglected. The coefficient of reduction used 
is 0.9, the one given by Dubuisson in his treatise on hydraulics. 

The main difficulty consists in measuring the difference of 
pressure of the atmosphere in the ash pit and that outside, 
for the depression in the flues in some cases does not exceed 
a few millimetres of water. Hirn's apparatus removes this 
difficulty. 

Burnat describes it as follows : 

When making a test the doors of the ash pit are removed 
and replaced by a piece of sheet iron, A (Fig. 37), which com- 
pletely shuts out all access of air except through the opening 
in the middle, to which is fitted the pipe CD, 13.8 inches 



146 



CALORIFIC POWER OF FUELS. 



diameter and 59 inches long. A tube leads from the front 
to the apparatus £, devised by Hirn, placed on a table or 
against the boiler-wall. This apparatus consists of a little 
gas holder whose upper surface is just one decimeter (3.9 




inches) on a side. Inside this and above the water level the 
tube A opens. The bell dips into a vessel of water and is 
suspended from a balance arm. 

The balance being in equilibrium when the atmospheric 
pressure acts on both sides of the bell, if the interior is con- 
nected with the ash-pit the weight needed to restore equili- 
brium will give a measure of the difference in pressure. The 
weight of half a gram (7.7 grains) represents one-twentieth 
millimetre (0.002 inch) of water. 

The formula adopted by Hirn is 



V= SX 



°v 



*g 



h X 0.76(1 + 0.0037/) 



0.0013^ 



in which 



V— volume of air introduced under the grate in cubic 

metres ; 
S = section in square metre of pipe-opening leading air to 

the ash-pit ; 
0.9 = coefficient of reduction; 



DASYMETER. 147 

h = difference of pressure expressed in height of water; 
B = barometric pressure in the room ; 
t = temperature of the room ; 
g = acceleration of gravity = 9.8088 metres. 

VOLUME BY AUTOMATIC APPARATUS. 

DASYMETER. 

Siegert and Durr * devised an apparatus called the 
Dasymeter, which has been introduced in several large works 
in Europe, where it gives satisfaction. 

It consists of a balance enclosed in a cast-iron box with 
a glass side (Fig. 36). At one end of the beam is a very 



Fig. 36. — Dasymeter. 

light glass balloon holding 2 to 3 litres, sealed by fusion. 
The other end carries a weight balancing the balloon. This 
weight is formed of a U-tube, //, containing mercury, and is 
open at one end; the other end is expanded into a bulb con- 
taining air, which is submitted to the variations of pressure 
and temperature through the mercury. If the pressure of 
the air increases or diminishes, the mercury rises or falls, and 
increases or diminishes the weight on the lever. Suppose an 

* Oesterreichische Zeitschrift fiir B.- und H.-Wesen, xvi. p. 291. 



148 CALORIFIC POWER OF FUELS. 

increase of pressure and a lowering of temperature whicli 
would diminish the density of the air one half. A corres- 
ponding quantity of mercury passes into the arm of the tube, 
and the original compensating weight is diminished by that 
amount. A graduated index shows the variations of weight, 
and hence the variations of density in the gases. An inge- 
nious arrangement allows regulation by rotating the U-tube 
on the axis pn. The tube is turned slowly around till 
adjusted, thus changing the length of the lever-arm. 

A difference of 1 per cent of carbonic acid causes a differ- 
ence in weight of 20 milligrams. One litre of air at 0° and 
760 millimetres weighs 1294 milligrams; 1 litre of carbonic 
acid weighs 1967 milligrams; the difference is 673 milligrams. 
If the gas contains 1 per cent of C0 2 , each litre increases 6.73 
milligrams in weight; and as the balloon contains 3 litres, it 
supports an external pressure of more than 3 X 6.73 = 20.19 
milligrams (0.31 1 grains). 

To prevent action of sulphurous acid the bearings are 
made of sapphire, onyx, bloodstone, etc., and metallic parts of 
phosphor-bronze. 

To set up the dasymeter, connect pipe e with the boiler- 
flue before the damper; the tube pleads to the chimney. By 
this means a current of gas passes through the box, and shows 
at any time the percentage of carbonic acid. Siegert gives 
the following results obtained with it, and the corresponding 
results by analysis : 

CQ j Dasymeter, 13.0, 13.0, 12.0, 6.25, 2.2, 16.3, 7.5, 12.5 
a \ Analysis, 13.0, 12.7, 12.2,6.00,2.0, 16.0,8.0, 13.0 

ECONOMETER. 

H. Arndt has invented what he calls the " Econometer" 
(Fig. 37), which, is on a similar principle.* It consists of a 
tight cast-iron shell, NN, containing a gas-balance. A pipe, 

* Zeitschrift des Vereines Deutscher Ingenieure, xxxvu. p. 801. 



ECONOMETER. 



149 



v', 0.4 inch in diameter leads to the inside of the flue before the 
damper; a second pipe, v" , communicates with the interior of 
the same flue beyond the damper. In the interior, the tube i' 
is connected to the upright pipe/", which leads the gas to bell 
/, and the tube i' to the tubulure g. i' and i" are of rubber. 




Fig. 37. — ECONOMETER. 

The balance is very sensitive, the beam carrying at one 
end the gas-holder e r , open bel6w and containing about 30 
cubic inches, and at the other end a second holder of similar 
size and weight as the first. Attached to the bottom of this 
one is a pan to hold the balancing weights. 

The tube/" conducts the gas to the balloon e' , which, open 
below, is freely movable in the cylinder g, by which it pro- 
duces suction in the tube i" . 

Carbonic acid being heavier than common air (1.96 to 
1.29) as well as the other associated gases, it follows that the 
density of the gases passing through the tubes depends on the 
carbonic acid content. The scale is divided so that each 
division shows one per cent of C0 2 in the gases. 



ISO 



CALORIFIC POWER OF FUELS. 



GAS-COMPOSIMETER. 

The gas-composimeter of Uehling is an apparatus for 
automatically and continuously determining the quantity of 
carbonic acid contained in waste gases. 

It is based on the laws governing the flow of gas through 
small apertures. 




Fig. 38. 

If two such apertures, A and B (Fig. 38), form respectively 
the inlet and outlet openings of chamber C, and a uniform 
suction is maintained in the chamber C by the aspirator D, 
the action will be as follows : 

Gas will be drawn through the aperture B into the cham- 
ber C, creating suction in chamber C, which in turn causes 
gas to flow through the aperture A. The velocity with 
which the gas enters through A depends on the suction in the 
chamber C, and the velocity at which it flows out through B 
depends upon the excess of the suction in chamber C over 
that existing in chamber C, that is, the effective suction in C. 
As the suction in C increases, the effective suction must 
decrease, and hence the velocity of the gas entering at A 
increases, while the velocity of the gas passing out through B 
decreases, until the same quantity of gas enters at A as passes 



TEMPERATURE OF THE WASTE GASES. 15 1 

out at B* As soon as this occurs no further change of suc- 
tion takes place in the chamber C, providing the gas entering 
at A and passing out at B be maintained at the same tem- 
perature. 

If from the constant stream of gas, while flowing through 
chamber C, one of its constituents is continuously removed by- 
absorption, a reduction of volume will take place in chamber 
C and cause an increase in suction, and consequently a de- 
crease in the effective suction in C . Hence the velocity of 
the gas through A will increase, and the velocity through B 
will decrease, until the same quantity of gas enters at A as 
is absorbed by the reagent, plus that which passes out at 
aperture B. 

Thus every change in the volume of the constituents we 
are absorbing from the gas causes a corresponding change of 
suction in the chamber C. 

The apparatus is connected with a regulator, a manom- 
eter, and automatic recording register. 

TEMPERATURE OF THE WASTE GASES. 

As in analyzing coal, cinders, and gases we must have 
average samples, so in treating of waste gases we need average 
temperatures. It is not enough to take the temperature 
occasionally with the thermometer; it varies too much from 
time to time, even if the readings are taken frequently. We 
must have some method of obtaining the average temperature 
of the gas current, and this can be accomplished by means of 
a heat reservoir introduced into the flue. 

For this purpose one was devised by Scheurer-Kestner of 
a type which has been repeatedly copied and modified. It 
consists of an iron tube, bb (Fig. 39), placed in the flue so 
that the upper end, covered with an insulating material, is let 
into the wall to about one half its thickness, the remainder 
hanging free in the flue. This tube is filled with paraffin, 



152 



CALORIFIC POWER OF FUELS. 



and in this is inserted the thermometer. The large mass of 
the paraffin is acted on by the mean temperature, but is unin- 
fluenced by any slight momentary changes which may occur. 
A self-registering thermometer is very advantageous, but 
readings at intervals of half an hour are sufficient ordinarily. 
Of course the opening around the tube should be packed so 
as to prevent all possible ingress of cold external air. 




Fig. 39. — Flue Thermometer. 

Occasionally mercury is used instead of paraffin. This 
renders the average of the heat more exactly, perhaps, but 
has the disadvantage of being much heavier and much more 
expensive. There are also many difficulties in handling it 
which do not obtain with paraffin. The paraffin should be 
well refined, and have a high melting-point. 



THE PNEUMATIC PYROMETER. 

Uehling's pneumatic pyrometer is based on a principle 
analogous to that of the gas-composimeter, and is now in use 
in many places, automatically measuring the temperatures of 
chimneys and furnaces for all temperatures up to 3000 F., 
and registering the same on cards. The apparatus has been 
tested at the Stevens Institute of Technology, and the 
indications pronounced reliable. It cannot be safely used 



THE PNEUMATIC PYROMETER. 153 

continuously for temperatures above 2500 , but at that tem- 
perature and lower it works well and satisfactorily for months 
without requiring any readjustment. The automatic register 
is very sensitive, and can be easily adjusted for a new range of 
temperatures at any time. 

An explanation of the principle of its working is given in 
the inventor's own words: 

' ' The Pneumatic Pyrometer is based on the laws govern- 
ing the flow of air through small apertures. 

"If two such apertures A and B (Fig. 38) respectively 
form the inlet and outlet openings of a chamber C, and a uni- 
form suction is created in the chamber C by the aspirator D, 
the action will be as follows : 

"Air will be drawn through the aperture B into the 
chamber C , creating suction in chamber C, which in turn 
causes air from the atmosphere to flow in through the aper- 
ture A. The velocity with which the air enters through A 
depends on the suction in the chamber C, and the velocity 
at which it flows out through B depends upon the excess of 
suction in C over that existing in the chamber C, that is, the 
effective suction in C . As the suction in C increases, the 
effective suction must decrease, and hence the velocity at 
which air flows in through the aperture A increases, and the 
velocity at which air flows out through the aperture B de- 
creases, until the same quantity of air enters at A as passes 
out at B. As soon as this occurs no further change of suc- 
tion can take place in the chamber C. 

"Air is very materially expanded by heat. Therefore 
the higher the temperature of the air the greater the volume, 
and the smaller will be the quantity of air drawn through a 
given aperture by the same suction. Now if the air as it 
passes through the aperture A is heated, but again cooled to 
a lower fixed temperature before it passes through the aper- 
ture B, less air will enter through the aperture A than is 
drawn out through the aperture B. Hence the suction in C 



154 CALORIFIC POWER OF FUELS. 

must increase and the effective suction in C must decrease, 
and in consequence the velocity of the air thiough A will 
increase and the velocity of the air through B will decrease, 
until the same quantity of air again flows through both aper- 
tures. Thus every change of temperature in the air entering 
through the aperture A will cause a corresponding change of 
suction in the chamber C. If two manometer-tubes/ and q y 
Fig. 38, communicate respectively with the chambers C and 
C, the column in tube q will indicate the constant suction in 
C and the column in tube/ will indicate the suction in the 
chamber C, which suction is a true measure of the tempera- 
ture of the air entering through the aperture A. 

DETERMINATION OF THE CARBON IN SMOKE. 

SOOT or black forms from quick cooling of the hydro- 
carbons, temporarily dissociated by high temperatures. Fuels 
having no hydrogen as hydrocarbons, never produce smoke ; 
pure charcoal, coke, or graphite never smokes. Soft coal, on 
the contrary, produces more as the air-supply grows less. 

Sainte-Claire Deville proved that a compound gas when 
heated sufficiently separates into its elements ; a sudden cool- 
ing now will give a simple mixture instead of the original 
combination. A slow cooling, however, reproduces the 
original gas. Berthelot proved, on the other hand, that new 
compounds are formed on heating the hydrocarbons to high 
temperatures, a part of the carbon being deposited as soot. 
These two phenomena undoubtedly go on together in smoke 
production.* 

If a metal tube be put in the gas current over a grate at 
a short distance from the fire, the hottest gases will be col- 

*Bunte gives some analyses of smoke-black: 

C H 

I... ... ...... . 97.2 2.8 

2 97-3 2.7 

3 98.5 1.5 



DETERMINATION OF THE CARBON IN SMOKE. 155 

lected. Pass a stream of cold water through a pipe in this 
gas-current and a large quantity of black will be deposited. 
On stopping the water flow and inclining the tube a little 
the carbon disappears gradually, and when the temperature 
of the tube attains that of the gas, no black will be deposited. 
Cool it again, and more black forms immediately. 

Combustion gases meet with surfaces relatively cold in 
the boiler sides or flues, or even in colder currents of gas or 
air passing in through the grate. This produces a quick cool- 
ing, and consequent formation of black. 

Experiments made at Mulhouse in 1859 by Burnat 
showed an advantage gained in steaming by producing smoke, 
rather than introducing too great excess of air. The experi- 
ments showed that the loss in carbon was quite small, and 
these results have been confirmed by others since. E. R. 
Tatlock of Glasgow finds 60 per cent combustible matter in 
soot, and obtained 51.46 grains per cubic foot of furnace 
gases. 

To determine the amount of carbon in smoke, Scheurer- 
Kestner used a glass organic analysis apparatus, the tube 
having in the middle loosely packed asbestos for about 8 
inches, which was kept in place by platinum spirals. One 
end was drawn out to connect with the absorption apparatus, 
and the other end placed in the flue. After igniting and 
cooling the asbestos the small end is connected with an 
aspirator and the gas drawn slowly through. The carbon is 
all stopped by the asbestos, which becomes black for a short 
distance. When sufficiently collected, dry the tube at ioo° 
C, heat to redness, and pass a stream of oxygen through it, 
collecting the carbonic acid formed. 

As an example Scheurer-Kestner gives the following: 

Waste gases, reduced to o° and 760 mm. 86 litres. 
Time of sampling 1 hour. 



156 CALORIFIC POWER OF FUELS. 

Composition of gas : 

C0 2 8.5 per cent. 

Excess of air ,. 53.4 

Nitrogen and residue 38.1 

C0 2 from the combustion 0.070 gram. 

Equivalent to carbon 0.019 " 

By the analysis of the gases and that of the coal the 
quantity of air consumed was calculated. Knowing the 
volume of air used for the coal, its composition, and the pro- 
portion of carbon as black in the gases, the loss due to such 
formation was calculated. 



Kind of Coal. 



Ruhr 



Hausham. 



Miesbach 



Waste Gases per 
Pound of Coal. 



ibic feet. 
135 
143 
169 
184 
189 
205 

163 

217 

233 

278 

293 
129 

155 



Black. 



Per Cubic Foot 
of Gas. 



grains. 
15-43 

7.41 

0.72 

6.74 

1. 19 

2.03 

20.49 

6.79 

5.71 
648 
3-70 
1.08 
6.64 



Per Cent Calories 
of Heat of 
Combustion. 



I.I 

0.6 

0.07 

0.2 

0.1 

0.1 

2.1 

0.8 

0.7 

1.0 

06 

O.I 

0.8 



Under the most unfavorable conditions for feeding the 
air, the loss due to formation of black does not exceed 2 per 
cent, even with smoky coal. Ronchamp coal gave the fol- 
lowing results : 

Feeding 240 cubic feet of air per pound of coal gave a 
gas containing 8.5 per cent of carbonic acid, excess of air 53 
per cent, and loss of carbon as black 0.485 per cent. 

Feeding 112 cubic feet of air per pound of coal gave a 



DETERMINATION OF THE CARBON IN SMOKE 1 57 

gas containing 14.8 per cent carbonic acid, 6.7 per cent excess 
of air, and 0.96 per cent of black. 

Saarbruck coal supplied with 155 cubic feet of air per 
pound gave a gas having 12.8 per cent of carbonic acid, 28.5 
per cent excess of air, and 2.03 per cent of black. 

These show that in addition to being a sign of diminution 
in combustible gases, smoke cannot cause a notable saving 
in fuel if such saving is accompanied by increased waste 
gases. The sensible heat of a larger volume compensates 
easily for the advantages resulting from the more perfect 
combustion of the carbon. 

Bunte publishes the following determinations of black: 

Several methods have been devised for approximating to 
the actual quantity of carbon contained in smoke. One is 
based on the amount of soot deposited on a given surface 
placed in the chimney. The soot deposits on the upper sur- 
face away from the direct current. After being exposed for 
a few hours the deposit is brushed off and weighed. Another 
method is by using smoked glasses of different degrees of 
opacity and ascertaining what depth of color is necessary to 
make the smoke invisible. An improvement on this method 
is now being worked out by one of our manufacturers of 
optical goods, by means of which the glasses are held in a 
tube and so arranged as to gradually produce the effect, and 
in such way that it can be measured. 

Another method is that devised by Ringelmann, by means 
of which the blackness of the smoke is compared with a set of 
ruled lines, so scaled in width of line and space as to produce 
six different gradations from smokeless through gray and 
gray-black to dead black. He recommends the preparation 
of cards 8 inches square, and have them suspended 50 feet 
from the observer, at which distance the individual lines 
become indistinct, and only a general tint is observable. The 
intensity of the smoke is then compared with the cards and re- 
corded as agreeing with card No. 1, 2, or whatever it may be. 



158 



CALORIFIC POWER OF FUELS. 



The cards are shown in Fig. 40, reduced in size, the actual 
lines and spaces being as follows: 



s 


5 


m 


mm 


m 


»wm 




H 


mm 


m 


h 


b 


a 


s 


n 


s 


H 


s 


1 






■ 




■ 
















































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































■■1 








zzztzzzxzzzzzzzzz: 


zzxzzzezzzzzzzzz: 




■ ■ 






1" 















..■■.....■■■■■■■.. 














Fig. 40. — Ringelmann Smoke Scale. 

Card o, all white. 

Card 1, black lines 1 mm. thick, 10 mm. apart between 
centres, leaving spaces 9 mm. square. 

Card 2, lines 2.3 mm. thick; spaces 7. J mm. sq. 
Card 3, lines 3.7 mm. thick; spaces 6.3 mm. sq. 
Card 4, lines 5.5 mm. thick; spaces 4.5 mm. sq. 
Card 5, all black. 



CHAPTER XII. 
CALCULATION OF THE HEAT UNITS. 

HEAT OF THE AQUEOUS VAPOR. 

The quantity of heat contained in a kilogram or pound of 
steam at any temperature is 

Q =z 606.5 + °-3C>5^ calories, 
or Q' = 1091.7 + 0.305O - 32) B. T. U., 

allowing the specific heat of water to be constant. The 
number of heat units is considered the same as the tem- 
perature. 

So that, allowing the average temperature of aqueous 
vapor to be 150 C, each kilogram at o° has absorbed a quan- 
tity of heat equal to 

606.5+0.305 X 150 = 652.25 calories 

or one pound has absorbed 1174 B. T. U. 

There is a correction to this, since we do not wish the 
units existing in the steam, but only those added to it from 
the fuel. We must then deduct that already existing in the 
water at its entrance to the boiler. If the feed-water be 20 
(68° F.) the formula becomes 

652.25 — 20 = 632.25 calories, 
or 1174— (68 - 32) = 1 138 B. T. U. 

159 



l6o CALORIFIC POWER OF FUELS 



HEAT OF WASTE GASES. 

The heat carried to the chimney by the waste gases is 
from several sources : 

1. Sensible heat shown by the temperature. 

2. Heat of vaporization of the hygroscopic water and the 
water formed from the hydrogen of the coal. 

3. Heat retained by the combustible gases or their heat of 
combustion. 

4. Heat represented by soot or black of the smoke. 

I. SENSIBLE HEAT OF THE TEMPERATURE. 

The calculation of the water equivalent of the heat carried 
to the chimney as sensible heat requires the volume, tem- 
perature, composition, and specific heat of the constituents. 

The specific heats of the usual constituents of waste gases 
are shown in Table VIII. The specific heats are supposed to 
be under constant pressure, so as to avoid useless calculations. 
The hydrocarbons or hydrogen will be omitted for the same 
reason. Calling v, v, v" ', v'" the volumes in cubic metres 
of the gases nitrogen, carbonic acid, carbonic oxide, and oxy- 
gen, we find their respective weights, by multiplying these 
volumes by the weight per cubic metre, 

1.2562/ 1.9662/ 1.25 12/' 1.4302/" 



N C0 2 CO O 

Multiplying these by the specific weights we obtain the value 
in water, 

C = 1.2562/ X 0.244+ 1.9662/' X 0.217 + 1. 2512/" X 0.245 + 
1. 4302/" X 0.217. 

The equivalent in water c multiplied by the temperature 
on leaving the boiler gives calories, 

C = c X T. 



CALCULATION OF THE HEAT UNITS. l6l 

A correction of the same kind as that applied to the tem- 
perature of the feed-water must be applied. We do not 
wish the total calories, only those taken up from the coal. 
From the observed temperature T we must deduct the 
original temperature / before entering the fire. So that 

C=cX{T-t). 

The general formula then becomes 

C = [(1.256^)0.244 + (1.966^)0.217 +( I - 2 5 I ^ // )°- 2 45 



N C0 2 CO 

+ (1.430^)0.217] (T-t). 



O 
As an example, suppose the following composition : 

Nitrogen 81.25 I _ j Air in excess 23.04 (4.84 X 4.761) 

Oxygen 4.84 ) ( Nitrogen 63. 05 (81.25 — 4.84— 23.04) 

Carbonic acid. . 13.08 13.08 

Carbonic oxide. 0.83 0.83 



and that the temperature (T — t) is 130 . Then 

Nitrogen 1.256 X .8125 X 0.244 = 0.249 

Carbonic acid 1.966 X . 1308 X 0.217 = °-°55 

Carbonic oxide. . . 1.25 1 X .0083 X 0.245 — 0.002 
Oxygen 1-430 X .0484 X 0.217 = 0.015 



1. 0000 0.321 

The value in water for 1 cubic metre is 0.321 kilogram, 
which at 130 give 

0.321 X 130 = 41.7 calories. 

If the volume of the gases was 8.938 cubic metres per 
kilogram of coal, the calories carried to the chimney would be 

8.938 x 41.7 



100 



372 calories. (669.6 B. T. U.) 



l62 



CALORIFIC POWER OF FUELS. 



The same result can be reached more quickly by taking 
the ratio of the specific heats to the volume (Table VIII). 

N 8125X0.306 = 0.249 

C0 2 1308 X 0.426 = 0.055 

CO 0083 X o. 306 = 0.002 

0484 X 0.310 = 0.015 

1. 0000 0.321 

0.321 X 130 X 8.938 = 372 calories. 

This may be still further simplified in practical work with 
the combustion under normal conditions. Base the calcula- 
tion on the proportion of carbonic acid, using 0.306 as coeffi- 
cient for the remaining gases. Then 

C = (0.426^ + o.3o6^)(r— /) 

v C0 2 0.1308 X 0.426 = 0.055 

R N, CO, and 0.8692 X 0.306 = 0.266 



0.321 

By means of the coefficients in Table IX we can still 
further shorten the calculation. By this table we get directly 

0.321 X 130 X 8.938 = 372 calories. 

The loss of heat due to temperature of the waste gases 
varies according to the condition of the boiler, its surface for 
radiation, the grate surface, and the air supply. With the 
most advantageous cases, and moderate combustion, the gas 
temperature at the exit does not exceed 150 (302° F.), and 
the loss, 5 or 6 per cent of the total heat of combustion. 
It may reach 10 per cent, and in some cases even more. 

2. HEAT OF THE HYGROSCOPIC AND COMBUSTION WATER. 

During combustion, coal furnishes a quantity of aqueous 
vapor from its hygroscopic water and its hydrogen ; the latter 



CALCULATION OF THE HEAT UNITS. 1 63 

is determined by multiplying the weight of hydrogen by 9. 
This is added to the hygroscopic water, and the formula 

(606.5 + O-3O50 — ? 

applied ; t being the temperature of the vapor in the gases 
(equal to that of the gases), and t' being that of the external 
air. Besides this, however, we must consider the specific 
heat of the aqueous vapor, 0.475. Each kilogram still 
absorbs 0.475 multiplied by the number of degrees of tem- 
perature above 100°, and the formula becomes 

.4(606.5 + 0.305/) — t' + 0.475^ - 100)], 

x being the quantity of water, in kilograms, furnished by the 
coal. 

Suppose a coal contains 15 grams per kilogram of hygro- 
scopic water and 45 grams of hydrogen, as follows: 

Hygroscopic water 15 

Carbon 735 

Hydrogen 45 

Nitrogen and oxygen 50 

Ash ' 1 60 

1000 

Hydrogen 45 produces 9 X 45 = 4°5 grams, to which 
add the 15 grams of hygroscopic water, 405 — |— 1 5 = 420 
grams. The heat necessary to vaporize this, increased by 
that corresponding to the temperature of the gases passing up 
the chimney, represents the heat lost. 

If the flue temperature is 145 ° = t, and the external air 
1 7. 5 = t' ', we have 

0.420K606.5 + 0.305 X 145) - 17.5 +0.475(145 - 100) 

= 274.9(494.8 B T.U.). 



164 CALORIFIC POWER OF FUELS. 

If the heat of combustion of the coal is 7000 calories, then 
the loss is 

274.9 

- = 3.02 per cent. 

7000 ° y v 

The loss due to these causes in an average coal (4-5 per 
cent hydrogen and 1 to 2 per cent moisture) is usually from 2 
to 4 per cent. 

3. CALORIES OF THE COMBUSTIBLE GASES. 

Carbonic oxide is always present in variable quantities, 
often hydrocarbons and sometimes hydrogen. This refers to 
ordinary fuel and the usual methods of burning. The quan- 
tity of unburnt gases depends on the kind of fireplace used 
and the system of charging. Thick charges of fuel always 
increase the volume of unburnt gases; the smallest amount 
being obtained from small, equivalent charges, fed frequently 
and using 30 to 50 per cent more air than the theoretical 
quantity. 

To determine this loss we may commence with the volume 
or the weight corresponding to 1 kilogram of coal burnt. 
The calculation is given on pages 437 and 138. No account 
need be made of the temperature, the calculation of loss due 
this having been made on page 16 1 for all gases, and there- 
fore for these gases. 

The calorific coefficients of the unburnt gases, referred to 
a cubic metre at 0° and 760 mm. pressure, are 



Heat of Combustion. 



Weight per cub. m. 
in Kilograms. 

Hydrogen 0.089 

Carbonic oxide 1.25 1 

Methane (CH 4 ) 0.715 

Carbon vapor 1.073 



r ■ 

Per Kilo. 


Per Cubic Metre. 


34500 


309I 


2435 


3043 


13343 


IOO38 


II328 


I2143 



CALCULATION OF THE HEAT UNITS. 1 65 

The weight and heat of combustion of carbon vapor are 
given, as most of the time we do not know the molecular 
condensation of the hydrocarbons ; usually the ultimate com- 
position is all that is known. Hence the hydrogen and car- 
bon must be given their heat values as though free. Fortu- 
nately they occur in only small percentages, and the error 
introduced by so doing is small. 

Suppose a gas to analyze 

Carbonic oxide 1.0 

Carbonic acid 13.0 

Methane 1 .0 

Oxygen 6.0 

Nitrogen 79.0 

100. o 

Assuming that the air has been fed at the rate of 10 cubic 
metres per kilogram (160.5 cubic feet per pound), and that 
the coal has a heat value of 8000 calories (14400 B. T. U.), 
we will have, for 10 cubic metres, 

Carbonic oxide o. 1 cubic metres. 

Carbonic acid 1.3 " " 

Methane o. 1 " 

Oxygen 0.6 " " 

Nitrogen 7.9 " " 



10. o 



Then 



CH 4 , 0.1 cub. m. @ 0.715 = 0.0715 kilogram; 
CO, 0.1 " " @ 1. 251 =0.1251 



and 0.0715 X 13343 = 933-7 calories; 

0.1251 X 2435 = 305.0 



Total ....1238.7 



1 66 CALORIFIC POWER OF FUELS. 

The loss, then, is 1238.7 in 8000, or 15.48 per cent. 

If instead of knowing the proportion of the hydrocarbons 
we know only that of carbon and hydrogen, the heat values 
calculate separately. Then, instead of methane o. 1, there 
would be carbon 0.05, and hydrogen 0.2. Then the cal- 
culation would be 



0.2 X 0.089 = 0.0178 
0.05 X 1.073 = 0.0536 
o. 1 X 1. 251 = 0.1251 



0.0178 X 34500 = 614. 1 
0.0536 X 8137 = 436.1 
0.1251 X 2435 = 305.0 



355.2 calories 



The difference, 1355.2 — 1238.7 = 116.5 calories, or 0.9 
per cent of the calories lost, or 15.48 X .009 = 0.138 per cent 
of the total calories of the coal, which is small compared with 
other sources of error. 

By employing Table VII we may dispense with reducing 
the volumes to weights, thus : 

Hydrogen 0.2m 3 X 3091 = 618 

Carbon vapor 0.05 x 8722 = 436 

Carbonic oxide . . . . o. 1 X 3043 = 304 



135: 



The preceding is an exaggerated case; as usually, with 
ordinary working, the loss is from 2 to 7 per cent, rarely 
exceeding the latter. Either method of calculation may be 
used, then, without risk of causing an error of importance. 

4. CALORIES DUE TO THE SOOT. 

The soot in smoke consists of carbon with a trace of 
hydrogen. It can be calculated as all carbon without appre- 
ciable error and with the coefficient 8137. Knowing the 
volume of gases produced by 1 kilogram and its content in 
black (page 154), calculate the number of calories. Under 



CALCULATION OF THE HEAT UNITS. 



167 



the most favorable conditions for smoke production the loss 
does not exceed 1 per cent, and is generally less than one 
half that amount. 

DISTRIBUTION OF CALORIES-LOSS. 

The difference between heat units accounted for and 
those possible is considered as resulting from radiation by 
surfaces not available for producing steam. The following is 
taken from Scheurer- Kestner's results with a three -tube 
steam boiler followed by a reheater. The first column gives 
results obtained with Ronchamp coal in 1868, the second 
results with Nixon's Navigation Co.'s coal in 1881. 



Ronchamp 

Calories in the steam 58 to 

1 a f waste gases 3.8 to 

1 ll " unburnt gases .. . 2.4 to 

' " " smoke 0.3 to 

' " li aqueous vapor. . 2.0 to 

* not accounted for 19.4 to 24 



•7 

•7 
•75 
•7 
•7 



Nixon. 

74-5^ 
5.42 

traces 
none 
2.81 

17.27 



On September 20, 1895, Engineering published the results 
of some experiments made by Bryan Donkin with Nixon's 
coal on twenty different types of boilers. The following 
table contains some of them : 



Calories. 



In the steam 

In the waste gases 

In the combustible gases.. 
Not accounted for 



XII. 

78.5 


VIII. 

78.3 


VI. 

74.4 


VII. 
71.8 


II. 


XI. 

69.8 


III. 


IV. 


XX. 


70.4 


67.6 


66.2 


65.8 


6.5 


14.0 


13.8 


13-3 


13.6 


18.0 


l6.2 


22.5 


18.0 


0.0 


1.7 


2.4 


0.8 


0.0 


1.2 


1.2 


0.0 


1.6 


15.0 


5.8 


9-3 


14.0 


11. 9 


IO.9 


9.6 


11. 


14.4 



63.8 

9.4 

12.7 

13.9 



The calories in the steam varied from 63.8 to 78.5 per cent. 

*' " " " waste gases " " 6.5 to 22.5 " " 

" 4< '• combustible gases " " 0.0 to 12.7 " " 

" " not accounted for " 5.8 to 15.0 " u 

For the method of properly tabulating the heat balance, 
see section XXI of the Steam Boiler Code on page 193. 



1 68 CALORIFIC POWER OF. FUELS. 

FLAME AND FLAME TEMPERATURES. 

Whenever the temperature is sufficiently high to raise a 
portion of the carbon, hydrogen, or other gaseous com- 
bustible to incandescence, flame is produced. The tempera- 
ture at which this phenomenon occurs varies with the sub- 
stance burnt. Usually it requires a red heat or higher, but 
in some cases a much lower temperature suffices: bor-methyl 
B(CH 3 ), is an example, the flame temperature of which is not 
high enough to scorch the finger placed in it. It is not neces- 
sary that the flame should have solid particles in it, as flame 
is produced by hydrogen burning under pressure in oxygen ; 
neither is incandescence alone sufficient, as the fire of pure 
carbon, magnesium, or iron glows but does not flame. 
Flame is hollow, the combustion occurring on the surface, 
and this may be easily demonstrated, by drawing off some of 
the interior unconsumed gases with a tube and burning them. 

Bunsen's researches led to the conclusion that the tem- 
perature of burning carbonic oxide rapidly rose to 3000 C, 
and remained stationary till one third of it was consumed ; 
the temperature then fell to 2500 C, at which more burnt; 
and finally fell to about 1200 C, which temperature was 
maintained till all the remainder was consumed. Actually 
the last temperature is soon reached in practice. Berthelot 
confirms this, but is in doubt whether the loss of. temperature 
is due to dissociation or to change in specific heat. Some 
hold that part of this loss of heat is caused by its absorption, 
due to the production of incandescence and its accompanying 
flame phenomena. A gas raised to incandescence gradually 
manifests each increment of heat till that point is reached, 
and beyond this no increase is noticed, all such further 
increase being consumed by the flame production. 

The rate of propagation of flame varies with the pressure 
and with the material burning. The most rapid rate with 
coal gas is when it is mixed with 5 parts of air; with marsh 



FLAME TEMPERATURES. 1 69 

gas, Z\ parts of air. It will be noticed that the proportion of 
oxygen is sensibly less than that required for perfect com- 
bustion. 

The luminosity depends on the compression of the gases 
or the air. Hydrogen burning in oxygen at ordinary pressure 
gives a flame hardly visible at all ; with a pressure of 20 atmos- 
pheres it becomes quite luminous. Arsenic in burning pro- 
duces quite a luminous flame at ordinary air pressure ; but 
hardly any in rarefied air. The same is true of carbonic 
oxide and other gases. The luminosity seems to be in direct 
proportion to the pressure. 

Luminosity seems to be greater with those substances 
which on burning produce dense vapors. Hydrogen and 
chlorine produce a vapor twice as heavy as water and the 
luminosity is much stronger than with the oxygen-hydrogen 
flame. Carbon and sulphur also produce heavy vapors and 
much light. Phosphorus burning in oxygen produces the 
dense heavy phosphoric anhydride and this is accompanied 
with an almost blinding light. 

The length of the flame ordinarily depends on the quantity 
of hydrogen, and consequently the hydrocarbons contained 
in, or generated from, the body consumed. With fuels con- 
taining high hydrocarbon percentages, flame of almost any 
desired length can be produced. This is especially the case 
with gases. 

The theoretical temperature of combustion, and hence of 
the flame, may be calculated by dividing the heat units pro- 
duced by the specific heats of the products formed. Of course, 
these theoretical temperatures are never reached in practice, 
but they serve as aids in determining the value of fuels for 
certain purposes. 

A few typical examples of these calculations will be given. 

1. Hydrogen. — Hydrogen burnt in oxygen produces 
29000 heat units (water considered as vapor); the specific 
heat of the aqueous vapor produced is 0.475. The hydrogen 



I70 CALORIFIC POWER OF FUELS. 

uses 8 times its weight of oxygen and generates 9 times the 
quantity of water. 
Then 

29000 =6727° C. 
9 X 0.479 

Bunsen and Sainte-Claire Deville showed that the highest 
temperature actually obtained is 2500 C, which may be in- 
creased to 2850 C. by a pressure of 10 atmospheres. 

The presence of nitrogen modifies the result materially. 
The quantity of oxygen required, obtained from air, would 
introduce 26.78 parts of nitrogen, the specific heat of which 
is 0.244. The equation would then be 

?°°° g =-" 2674° C. 

9 X 0.479 + 26.78 X 0.244 

Bunsen's maximum temperature actually reached was 
1800 C. 

2. Carbon. — Carbon burnt to carbonic oxide consumes 
1.33 parts of oxygen, forms 2.33 parts of carbonic oxide, and 
if burnt in air, introduces 4.46 parts of nitrogen. The specific 
heat of carbonic oxide is 0.245 an d of nitrogen 0.244, as 
before. The heat units generated are 2435. 

For combustion in oxygen the equation would be 

2435 



2.33 X 0.245 
In air it would be 

2435 



= 4265° C. 



= I462°C. 



2.33 X 0.245 +4-4 6 X 0.244 
The latter temperature is about the same as that actually 
observed, and shows that but little dissociation occurs. 
Owing to the non-volatility of carbon no flame is produced, 
only an incandescence. The flame we ordinarily see on in- 
candescent carbon is from the burning of carbonic oxide. 
Carbon burnt to carbon dioxide can be treated similarly ; also 
carbonic oxide burnt to carbon dioxide. 



FLAME TEMPERATURES. 1 71 

3. Marsh Gas. — This gas requires 4 times its weight of 
oxygen, and produces 2.25 parts of aqueous vapor and 2.75 
parts of carbonic acid. If air is used, 13.39 P art s of nitrogen 
are introduced. The heat of combustion is 13343 calories. 

The equations are, then, 

^43 = ? o c 

2.25 X 0.479 + 2.75 X 0.217 
for oxygen and 

-ilM3 _ 2245 o Cr 

2.25 X 0.479 + 2 -75 X 0.217 + 13.39 X 0.244 
for combustion in air. 

defiant gas, acetylene, etc., can be calculated similarly. 
With a mixed gas, i.e., one containing several gases, account 
must be taken of each one separately. Producer gas will be 
given as an example. 

4. Producer Gas. — The producer gas taken will be assumed 
to have the following composition by volume : 

Carbonic oxide. . 21.0 per cent. 

Hydrogen 11.5 " " 

Marsh gas 2.0 " " 

Carbonic acid 6.0 ' ' " 

Nitrogen. 59.5 " " 

100. o " " 
First obtain the weight of the constituents. (See the tableso) 
0.21 X 1. 2515 — 0.2628 
0.115 X 0.0896=0.0103 
0.02 X 0.7155 =0.0143 
0.06 X 1.9666=0.1360 
0.595 X 1. 2561 =0.7474 

C0 2 H 2 N 

CO O.2628 produces. .. . 0.413 .... 0.502 

H 0.0103 " 0.093 0.276 

CH 4 0.0143 " ..., 0.039 0.032 0.192 

C0 2 0.1360 " 0.136 

N 0.7474 " .... .... .... 0.747 

0.588 0.125 1. 717 



I?2 CALORIFIC POWER OF. FUELS, 

Then as the heat of combustion is 747.66 by volume or 
874.6 by weight, we have for combustion in oxygen, 

*-l±t = 235 o° C, 

0.125 x 0.479 + 0.588 X 0.217+ 0.747 X 0.244 

and for combustion in air, 

?Z±6 = III2 ° C 

0.125 X 0.479 + 0.588 X 0.217+ 1. 717 X 0.244 

5. Petroleum Oil. — The oil may be assumed to contain 

Carbon 85 per cent. 

Hydrogen 15 " " 

100 

C 0.85 produces 3.ii7CO a and 7.588 N 

H 0.15 " 1.35 H 2 .... " " 4.017 " 



1.35 H 2 1.117 C0 2 11.605 N 

The heat of combustion may be assumed at 10000 calories. 
Then for combustion in oxygen, 

10000 nn „ 

= 7558°C, 



1.35 X 0.479+ 3- 117 X 0.217 

and for combustion in air, 

1 0000 
1-35 X 0.479+ 3. 117 X 0.217+ 11.605 X 0.244 



2400 c. 



Other oils or solid fuels may be calculated according to 
this model. 

At the end of the volume are given a few of those fuels 
most commonly used with the theoretical oxygen and air 
flame temperatures. 



CARBON VAPOR. 173 

WEIGHT AND HEAT UNITS OF CARBON VAPOR. 

Two volumes of carbonic oxide are produced from I volume 
of oxygen, and hence from I volume of carbon. I cubic 
metre of carbonic oxide weighs 125 1 grams. 1 cubic metre 
of oxygen weighs 1430 grams. 1 cubic metre of carbonic 
oxide contains, then, one-half a cubic metre of oxygen weigh- 
ing 7 X 5 grams, and one-half a cubic metre of carbon vapor 
weighing 536 grams. Hence I cubic metre of carbon vapor 
weighs 2 X 536 = 1072 grams, and 1 kilogram measures 
1 : 1072 = 0.9328 cubic metre. 
Or 

1 cubic foot of carbonic oxide weighs 546.78 grains. 
1 " " " oxygen weighs 624.85 " 

One cubic foot CO then contains £ cubic foot of O and \ 
cubic foot of C. 

546.78 - 312.425 = 234.355, 
and 

2 X 234.355 = 468.71 grains, 

weight of 1 cubic foot of carbon vapor. 

One pound of carbon vapor measures 14.93 cubic feet. 

If we wish the heat-units of carbon in vapor without the 
heat of vaporization, multiply the weight of a cubic metre by 
the heat of combustion of solid carbon. If from wood charcoal, 

8137 X 1.072 = 8722(15699.6 B. T. U.). 

If from diamond, 

7859 X 1.072 = 8424(14963.2 B.T. U.). 

If carbon vapor with its heat of vaporization be wanted, 
take the heat of combustion of carbonic oxide which contains 
carbon as vapor and compare it with the heat of combustion of 
carbon, uniting with the same quantity of oxygen to form 



174 CALORIFIC POWER OF FUELS. 

carbonic oxide. In doing so it is supposed that carbon in 
combining with two atoms of oxygen generates the same 
quantity of heat with one as with the other, only in the first 
case part of the heat is used in vaporizing the carbon. This 
heat is found by subtracting the heat of combustion of the 
solid carbon from that of the carbon supposed gaseous in 
carbonic oxide. 

One kilogram of carbon unites with 1.333 kilograms of 
oxygen to form 2.333 kilograms of carbonic oxide. With 
diamond there is generated 2405 calories. The 2.333 kilograms 
of carbonic oxide in becoming carbonic acid generates 2.333 X 
2435 = 5680 calories. Then 1 kilogram of carbon in passing 
from carbonic oxide to carbonic acid generates 5680 calories. 
We have seen, on the other hand, that I kilogram of diamond 
carbon generates 2405 calories in becoming carbonic oxide. 
The difference, then, 5680 — 2405 = 3275(5895 B. T. U.) cal- 
ories, represents the heat of vaporization of diamond carbon. 
With wood charcoal it becomes 5680 — 2489 — 3191(5743.8 

B. T.U.). 

The heat of combustion will be then 7859 -f- 3275 = 1 1 134 
calories (20041 B. T. U.) for diamond, and 8137 + 3 191 = 
1 1 328 calories (20390 B. T. U.) for wood charcoal. 

EVAPORATIVE POWER OF FUEL. 

The evaporative power of a fuel represents the number of 
pounds of water at 21 2° F. that can be evaporated or con- 
verted into steam by one pound of the fuel. Water at that 
temperature is sufficiently heated to vaporize, but needs an 
addition of force equivalent to that required for the vaporiza- 
tion. This quantity varies for the pressure of the barometer 
and the temperature of the water, but for the purposes of cal- 
culation is considered to be taken at 30 inches of mercury and 
212 F. Experiment has shown the equivalent to be 965.7 
heatunits (B. T. U.). 



EVAPORATIVE POWER. 175 

To find the theoretical evaporating power of a fuel, then, 
divide the number of thermal units it generates on combus- 
tion by 965.7. For instance, the heat of combustion of a 
sample of Illinois coal was determined by Prof. Carpenter to 
be 13200. Its evaporative power would be 

13200 

0^= I 3- 6 7 pounds. 

This means that under the proper conditions one pound 
of the coal in question would evaporate 13.67 pounds already 
heated to 212 F. 

But this amount of duty is rarely realized. The boiler 
.may not be well built, the setting may be faulty, and there 
are numerous other chemical or mechanical conditions which 
modify the yield. With these no rule can be established ; 
each individual case must be allowed for specially. With 
ashes and moisture, chemical constituents of the coal, the 
case is different. A percentage allowance for these will usually 
suffice. 

For instance, in the above coal there was 5.12 per cent of 
water and 15.2 per cent of ash. Then 

100 — (15.2 -j- 5.12) X 13.67 = 12.23 pounds. 

If deemed necessary, a further correction can be made for 
the water of the coal, which would reduce the evaporation by 
its own amount. This correction would become 

12.23 — 0.05 = 12.18 pounds 

as the quantity which should be evaporated with the coal as 
analyzed. 

The quantity of ash produces an effect on the evaporative 
power aside from its proportional reduction in combustible. 
This is due to the fact that where a large percentage of ash 
occurs, the particles of carbon of the fuel are not burnt com- 



iy6 CALORIFIC POWER OF FUELS. 

pletely, owing to being enclosed in the ash and consequently 
shut off from access of air. This is especially the case with 
those ashes which are easily fuzed by the heat of the fire. 
Ashes containing carbonates are much more easily fuzed than 
those containing phosphates or sulphates. On this account a 
chemical analysis of the ash is at times quite desirable. 

Some difference in evaporation is noticed in using the dif- 
ferent sizes of coal, more particularly with the fine sizes. 
With the proper arrangements for burning fires a good yield 
is obtained, but with the ordinary grates the yield is much 
tower. 



APPENDIX. 



REPORT OF THE COMMITTEE ON THE REVISION OF THE 
SOCIETY CODE OF 1885, RELATIVE TO A STANDARD 
METHOD OF CONDUCTING STEAM-BOILER TRIALS. 

Presented to the New York meeting of the American Society of Mechani- 
cal Engineers, December, 1897, and forming a part of the Transac- 
tions, Volume XIX. 

To the American Society of Mechanical Engineers. 

Gentlemen : The undersigned Committee, to which was 
submitted the revision of the Society Code of 1885, relative 
to a standard method of conducting steam-boiler trials, 
reports as follows : 

The former Committee gave a full statement of the prin- 
ciples which governed it in the preparation of the Code of 
Rules at that time recommended. These principles covered 
the ground in an admirable manner, so far as the practice of 
boiler-testing had been perfected, and we are in unanimous 
accord with the sentiments which the report of that Com- 
mittee expressed. During the interval of twelve years which 
has passed, methods and instruments have in some measure 
changed. Improvements have been made in the instruments 
for determining the moisture in steam. The throttling and 
separating form of calorimeters have displaced the barrel and 
other types of steam calorimeters referred to in the previous 
report. Attention has been devoted to the determination of 
the calorific value of coal, and a number of coal calorimeters 

177 



I78 APPENDIX. 

have been brought out and successfully used for this purpose. 
It has come to be a practice with many experts to include 
in the table of results of boiler-tests the percentage of 
" efficiency," or proportion of the calorific value of the coal 
which is utilized by the boiler. Specifications and contracts 
are in some cases drawn up, providing for certain percentages 
of efficiency instead of a specified evaporation. The analysis 
of flue-gases is receiving more attention than formerly, not 
only in our educational institutions, but also in the regular 
practice of engineers who make a specialty of boiler-testing. 

Your Committee submits a revised Code, termed the Code 
of 1897. It is substantially the same as the 1885 Code, with 
such amendments as the experience of the last twelve years 
has shown to be desirable. 

It is beyond the province of the Committee to recom- 
mend instruments of particular makers for obtaining the 
quality of the steam, the calorific value of the fuel, or any 
other data relating to the trial ; but following the practice of 
the former Committee, individual members have submitted 
their views (with the approval of the full membership) in an 
" Appendix to the 1897 Code," signed by their initials. In 
this appendix are included some of the articles from the 
appendix to the former Code, which are thought to be of 
especial value. 

In the matter of instruments for determining the calorific 
value of fuel, it seems desirable that the Committee should 
make a recommendation which is as specific as present knowl- 
edge and circumstances will warrant. It is agreed that some 
form of calorimeter in which the coal is burned in an atmos- 
phere of oxygen gas is to be preferred, and it is generally 
held that the most perfect apparatus thus far brought out is 
the Bomb Calorimeter, originally designed by Berthelot, and 
modified by Mahler and Hempel. Several of these instru- 
ments are in use in this country, principally in the laborato- 
ries of engineering schools ; but the apparatus is complicated 



APPENDIX. 179 

and expensive, and it is not probable that many engineers 
will have the instrument as a part of their equipment for test- 
ing boilers. It is recommended, therefore, that samples of 
the coal used in testing boilers be sent for determinations of 
their heating value to a testing laboratory provided with one 
of these instruments, or with some instrument which shall be 
proven to be equally good. 

Besides the amendments to the Code of 1885, concerning 
the determination of "efficiency " and the use of improved 
steam calorimeters, directions are given for sampling the coal, 
for determining the heat of combustion from the chemical 
analysis of coal, and for working out a heat balance. Rules 
are laid down for finding the quantity of moisture in coal and 
for making allowance for it. The tabular form of presenting 
the results of the test is somewhat changed from that of the 
Code of 1885, and alterations in the text of that Code are 
made wherever revision seems desirable. 

The Committee approves the conclusions of the Com- 
mittee of 1885 concerning the standard " unit of evapora- 
tion " contained in the following extract from the introduction 
to the Code of 1885 : 

" It has gradually come to be the custom to reduce all 
results to the common standard of weight of water evaporated 
by the unit weight of fuel, the evaporation being considered 
to have taken place at mean atmospheric pressure, and at the 
temperature due that pressure, the feed-water being also 
assumed to have been supplied at that temperature. This is, 
in technical language, said to be the ' equivalent evaporation 
from and at the boiling-point' (212 degrees Fahr.), and has 
now become so generally incorporated into the science and 
the practice of steam-engineering that your Committee would 
simply express their approval of the adoption, and recom- 
mend the permanent retention of this * unit of evaporation,' 
viz., one pound of water at 212 degrees Fahr. evaporated 
into steam of the same temperature. This is equivalent to 



ISO APPENDIX. 

the utilization of 965.7 British thermal units per pound of 
water so evaporated." 

The unit of commercial boiler horse-power adopted by 
the Committee of 1885 was the same as that used in the re- 
ports of the boiler-tests made at the Centennial Exhibition 
of 1876. The Committee of 1885 reported in favor of this 
standard in language of which the following is an extract : 

"Your Committee, after due consideration, has deter- 
mined to accept the Centennial standard, and to recommend 
that in all standard trials the commercial horse-power be 
taken as an evaporation of 30 pounds of water per hour 
from a feed-water temperature of 100 degrees Fahr. into 
steam at 70 pounds gauge-pressure, which shall be consid- 
ered to be equal to 34^ units of evaporation ; that is, to 34^ 
pounds of water evaporated from a feed-water temperature 
of 212 degrees Fahr. into steam at the same temperature. 
This standard is equal to 33,305 thermal units per hour." 

The present Committee accepts the same standard, but 
reverses the order of two clauses in the statement, and 
slightly modifies them to read as follows : 

In all standard trials the commercial horse-power shall 
be taken as 344- units of evaporation; that is, 34-J pounds 
of water evaporated from a feed- water temperature of 212 
degrees Fahr. into steam at the same temperature. This 
standard is equivalent to 33,317 British thermal units per 
hour. It is also practically equivalent to an evaporation of 
30 pounds of water from a feed-water temperature of 100 
degrees Fahr. into steam at 70 pounds gauge-pressure.* 

* According to the tables in Porter's Treatise on the Richards Steam- 
engine Indicator, an evaporation of 30 pounds of water from 100 degrees 
Fahr. into steam at 70 pounds pressure is equal to an evaporation of 34.488 
pounds from and at 212 degrees; and an evaporation of 34! pounds from 
and at 212 degrees Fahr. is equal to 30.010 pounds from 100 degrees Fahr. 
into steam at 70 pounds pressure. 

The "unit of evaporation" being equal to 965.7 thermal units, the 
commercial horse-power = 34.5 X 965.7 = 33.317 thermal units. 



APPENDIX. 10 1 

The Committee also indorses the statement of the Com- 
mittee of 1885 concerning the commercial rating of boilers, 
changing somewhat its wording, so as to read as follows : 

"It is the opinion of this Committee that a boiler rated 
at any stated horse-power should develop, that power when 
using the best coal ordinarily sold in the market where the 
boiler is located, fired by an ordinary fireman, with a draft at 
the smoke-box not exceeding f inch of water column ; and, 
further, that the boiler should develop at least one third 
more than its rated power when operated with the best sys- 
tem of firing and with the full draft available." 
Respectfully submitted, 

Chas. E. Emery,* 

Wm. Kent, 

Geo. H. Barrus, 

Chas. T. Porter, 

Robert H. Thurston, ^Committee. 

Robert W. Hunt, 

F. W. Dean, 

J. S. Coon, 

Wm. B. Potter, 

RULES FOR CONDUCTING BOILER-TRIALS, 
CODE OF 1897. 

Preliminaries to a Trial. 

I. Determine at the outset the specific object of the pro- 
posed trial, whether it be to ascertain the capacity of the 

* The motion for the appointment of this Committee was made by Mr. 
Barrus in connection with the discussion of Mr. Dean's paper, No. DCL, 
on " The Efficiency of Boilers," etc. The President of the Society desig- 
nated Mr. Kent, the chairman of the Committee of 1884, to call the first 
meeting of the new Committee. At that meeting, on motion of Mr. Kent, 
Dr. Emery was selected as chairman, and he conducted the preliminary 
correspondence. The report in the form originally printed was prepared 
"by a sub-committee consisting of Messrs. Emery, Porter, Barrus, and 
Kent. 



1 82 APPENDIX. . 

boiler, its efficiency as a steam-generator, its efficiency and its 
defects under usual working conditions, the economy of some 
particular kind of fuel, or the effect of changes of design, 
proportion, or operation ; and prepare for the trial accord- 
ingly. 

II. Examine the boiler, both outside and inside; ascertain 
the dimensions of grates, heating-surfaces, and all important 
parts; and make a full record, describing the same, and illus- 
trating special features by sketches. The area of heating 
surface is to be computed from the outside diameter of all 
tubes, whether water-tubes or fire-tubes. This rule corre- 
sponds to the practice of many builders of different types of 
boilers, and is intended to make the practice of rating heating- 
surface uniform. All surfaces below the mean water-level 
which have water on one side and products of combustion on 
the other are to be considered as water-heating surface, and 
all surfaces above the mean water-level which have steam on 
one side and products of combustion on the other are to be 
considered as superheating surface. 

III. Notice the general condition of the boiler and its 
equipment, and record such facts in relation thereto as bear 
upon the objects in view. 

If the object of the trial is to ascertain the maximum 
economy or capacity of the boiler as a steam-generator, the 
boiler and all its appurtenances should be put in first-class 
condition. Clean the heating-surface inside and outside, 
remove clinkers from the grates and from the sides of the fur- 
nace. Remove all dust, soot, and ashes from the chambers, 
smoke-connections, and flues. Close air-leaks in the masonry 
and poorly fitted cleaning-doors. See that the damper will 
open wide and close tight. Test for air-leaks by firing a few 
shovels of smoky fuel and immediately closing the damper, 
observing the escape of smoke through the crevices. 

IV. Determine 'the character of the coal to be used. For 
tests of the efficiency or capacity of the boiler the coal should,. 



APPENDIX. 183 

if possible, be of some kind which is commercially regarded 
as a standard. For New England and that portion of the 
country east of the Allegheny Mountains, good anthracite egg 
coal, containing not over 10 per cent of ash, and semi- 
bituminous Cumberland (Md.) and Pocahontas (Va.) coals are 
thus regarded. West of the Allegheny Mountains, Poca- 
hontas (Va.) and New River (W. Va.) semi-bituminous, and 
Youghiogheny or Pittsburg bituminous coals are recognized 
as standards.* There is no special grade of coal mined in 
the Western States which is widely recognized as of superior 
quality or considered as a standard coal for boiler-testing. 
Big Muddy lump, an Illinois coal mined in Jackson County, 
111., is suggested as being of sufficiently high grade to answer 
the requirements in districts where it is more conveniently 
obtainable than the other coals mentioned above. 

V. Establish the correctness of all apparatus used in the 
test for weighing and measuring. These are : 

1. Scales for weighing coal, ashes, and water. 

2. Tanks or water-meters for measuring water. Water- 
meters, as a rule, should only be used as a check on other 
measurements. For accurate work, the water should be 
weighed or measured in a tank. 

3. Thermometers and pyrometers for taking temperatures 
of air, steam, feed-water, waste gases, etc. 

4. Pressure-gauges, draft-gauges, etc. 

The kind and location of the various pieces of testing 
apparatus must be left to the judgment of the person con- 
ducting the test, always keeping in mind the main object, 
i.e., to obtain authentic data. 

VI. See that the boiler and chimney are thoroughly heated 
before the trial to their usual working temperature. If the 

* These coals are selected because they are about the only coals which 
contain the essentials of excellence of quality, adaptability to various kinds 
of furnaces, grates, boilers, and methods of firing, and wide distribution 
and general accessibility in the markets. 






1 84 APPENDIX. 

boiler is new and of a form provided with a brick setting, it 
should be in regular use at least a week before the trial, so as 
to dry and heat the walls. If it has been laid off and become 
cold, it should be worked before the trial until the walls are 
well heated. 

VII. The boiler and connections should be proved to be 
free from leaks before beginning a test, and all water connec- 
tions, including blow and extra feed-pipes, should be discon- 
nected, stopped with blank flanges, or bled through special 
openings beyond the valves, except the particular pipe through 
which water is to be fed to the boiler during the trial. Dur- 
ing the test the blow-off and feed-pipes should remain ex- 
posed. 

If an injector is used, it should receive steam directly 
through a felted pipe from the boiler being tested.* 

See that the steam-main is so arranged that water of con- 
densation cannot run back into the boiler. 

VIII. Starting and Stopping a Test. — A test should last 
at least ten .hours of continuous running. A longer test may 
be made when it is desired to ascertain the effect of widely 
varying conditions, or the performance of a boiler under the 
working conditions of a prolonged run. The conditions of 
the boiler and furnace in all respects should be, as nearly as 
possible, the same at the end as at the beginning of the test. 
The steam-pressure should be the same ; the water-level the 
same ; the fire upon the grates should be the same in quan- 
tity and condition; and the walls, flues, etc., should be of 
the same temperature. Two methods of obtaining the de- 

* In feeding a boiler undergoing test with an injector taking steam 
from another boiler, or the main steam-pipe from several boilers, the 
evaporative results may be modified by a difference in the quality of the 
steam from such source compared with that supplied by the boiler being 
tested, and in some cases the connection to the injector may act as a drip 
for the main steam-pipe. If it is known that the steam from the main 
pipe is of the same quality as that furnished by the boiler undergoing the 
test, the steam may be taken from such main pipe. 



APPENDIX. 185 

sired equality of conditions of the fire may be used, viz. : 
those which were called in the Code of 1885 "the standard 
method" and "the alternate method," the latter being em- 
ployed where it is inconvenient to make use of the standard 
method. 

IX. Standard Method. — Steam being raised to the work- 
ing pressure, remove rapidly all the fire from the grate, close 
the damper, clean the ash-pit, and as quickly as possible start 
a new fire with weighed wood and coal, noting the time and 
the water-level while the water is in a quiescent state, just 
before lighting the fire. 

At the end of the test remove the whole fire, which has 
been burned low, .clean the grates and ash-pit, and note the 
water-level when the water is in a quiescent state, and record 
the time of hauling the fire. The water-level should be as 
nearly as possible the same as at the beginning of the test. 
If it is not the same, a correction should be made by com- 
putation, and not by operating the pump after the test is 
completed. 

X. Alternate Method. — The boiler being thoroughly 
heated by a preliminary run, the fires are to be burned low 
and well cleaned. Note the amount of coal left on the grate 
as nearly as it can be estimated ; note the pressure of steam 
and the water-level, and note this time as the time of starting 
the test. Fresh coal which has been weighed should now be 
fired. The ash-pits should be thoroughly cleaned at once 
after starting. Before the end of the test the fires should be 
burned low, just as before the start, and the fires cleaned in 
such a manner as to leave the bed of coal of the same depth, 
and in the same condition, on the grates as at the start. The 
water-level and steam-pressures should previously be brought 
as nearly as possible to the same point as at the start, and 
the time of ending of the test should be noted just before 
fresh coal is fired. If the water-level is not the same as at 



1 86 APPENDIX. 

the start, a correction should be made by computation, and 
not by operating the pump after the test is completed. 

XI. Uniformity of Conditions. — In all standard trials the 
conditions should be maintained uniformly constant. Ar- 
rangements should be made to dispose of the steam so that 
the rate of evaporation may be kept the same from beginning 
to end. This may be accomplished in a single boiler by 
carrying the steam through a waste steam-pipe, the discharge 
from which can be regulated as desired. In a battery of 
boilers in which only one is tested the draught can be regu- 
lated on the remaining boilers, leaving the test-boiler to work 
under a constant rate of production. 

Uniformity of conditions should prevail as to the pressure 
of steam, the height of water, the rate of evaporation, the 
thickness of fire, the times of firing and quantity of coal fired 
at one time, and as to the intervals between the times of 
cleaning the fires. 

XII. Keeping the Records. — Take note of every event 
connected with the progress of the trial, however unimpor- 
tant it may appear. Rec@rd the time of every occurrence 
and the time of taking every weight and every observation. 

The coal should be weighed and delivered to the fireman 
in equal proportions, each sufficient for not more than one 
hour's run, and a fresh portion should not be delivered until 
the previous one has all been fired. The time required to 
consume each portion should be noted, the time being re- 
corded at the instant of firing the last of each portion. It is 
desirable that at the same time the amount of water fed into 
the boiler should be accurately noted and recorded, including 
the height of the water in the boiler, and the average pressure 
of steam and temperature of feed during the time. By thus 
recording the amount of water evaporated by successive por- 
tions of coal, the test may be divided into several periods if 
desired, and the degree of uniformity of combustion, evapo- 
ration, and economy analyzed for each period. In addition 



APPENDIX. 1 8/ 

to these records of the coal and the feed-water, half-hourly 
observations should be made of the temperature of the feed- 
water, of the flue gases, of the external air in the boiler-room, 
of the temperature of the furnace when a furnace-pyrometer 
is used, also of the pressure of steam, and o"f the readings of 
the instruments for determining the moisture in the steam. 
A log should be kept on properly prepared blanks containing 
columns for record of the various observations. 

When the " standard method" of starting and stopping 
the test is used, the hourly rate of combustion and of evapo- 
ration and the horse -power may be computed from the 
records taken during the time when the fires are in active 
condition. This time is somewhat less than the actual time 
which elapses between the beginning and end of the run. 
This method of computation is necessary, owing to the loss 
of time due to kindling the fire at the beginning and burning 
it out at the end. 

XIII. Quality of Steam. — The percentage of moisture in 
the steam should be determined by the use of either a throt- 
tling or a separating steam-calorimeter. The sampling-nozzle 
should be placed in the vertical steam-pipe rising from the 
boiler. It should be made of ^-inch pipe, and should extend 
across the diameter of the steam-pipe to within half an inch 
of the opposite side, being closed at the end and perforated 
with not less than twenty -g-inch holes equally distributed 
along and around its cylindrical surface, but none of these 
holes should be nearer than \ inch to the inner side of the 
steam -pipe. The calorimeter and the pipe leading to it 
should be well covered with felting. Whenever the indica- 
tions of the throttling or separating calorimeter show that the 
percentage of moisture is irregular, or occasionally in excess 
of three per cent, the results should be checked by a steam- 
separator placed in the steam-pipe as close to the boiler as 
convenient, with a calorimeter in the steam-pipe just beyond 
the outlet from the separator. The drip from the separator 



1 88 APPENDIX. . 

should be caught and weighed, and the percentage of moist- 
ure computed therefrom added to that shown by the calo- 
rimeter. 

Superheating should be determined by means of a ther- 
mometer placed in a mercury-well or oii-well inserted in the 
steam-pipe. 

For calculations relating to quality of steam and correc- 
tions for quality of steam. 

XIV. Sampling tJie Coal and Determining its Moisture. — 
As each barrow-load or fresh portion of coal is taken from the 
coal-pile, a representative shovelful is selected from it and 
placed in a barrel or box in a cool place and kept until the 
end of the trial. The samples are then mixed and broken 
into pieces not exceeding one inch in diameter, and reduced 
by the process of repeated quartering and crushing until a 
final sample weighing about five pounds is obtained, and the 
size of the larger pieces are such that they will pass through 
a sieve with J-inch meshes. From this sample two one- 
quart, air-tight glass preserving-jars, or other air-tight vessels 
which will prevent the escape of moisture from the sample, 
are to be promptly filled, and these samples are to be kept 
for subsequent determinations of moisture and of heating 
value, and for chemical analyses. During the process of 
quartering, when the sample has been reduced to about ioo 
pounds, a quarter to a half of it may be taken for an approxi- 
mate determination of moisture. This may be made by 
placing it in a shallow iron pan, not over three inches deep, 
carefully weighing it, and setting the pan in the hottest place 
that can be found on the brickwork of the boiler setting or 
flues, keeping it there for at least twelve hours, and then 
weighing it. The determination of moisture thus made is 
believed to be approximately accurate for anthracite and 
semi-bituminous coals, and also for Pittsburg or Youghio- 
gheny coal ; but it cannot be relied upon for coals mined 
west of Pittsburg, or for other coals containing inherent 



APPENDIX. 189 

moisture. For these latter coals it is important that a more 
accurate method be adopted. The method recommended by 
the Committee for all accurate tests, whatever the character 
of the coal, is described as follows : 

Take one of the samples contained in the glass jars, crush 
the whole of it by running it through an ordinary coffee-mill 
adjusted so as to produce somewhat coarse grains (less than 
T V inch), thoroughly mix the crushed sample, select from it a 
portion of from 10 to 50 grams, weigh it in a balance which 
will easily show a variation as small as 1 part in 1000, and 
dry it in an air or sand bath at a temperature between 240 
and 280 degrees Fahr. for one hour. Weigh it and record 
the loss, then heat and weigh it again repeatedly, at intervals 
of an hour or less, until the minimum weight has been 
reached and the weight begins to increase by oxidation of a 
portion of the coal. The difference between the original and 
the minimum weight is taken as the moisture. This moisture 
should preferably be made on duplicate samples, and the 
results should agree within 0.3 to 0.4 of one per cent, the 
mean of the two determinations being taken as the correct 
result. 

If the coal contains an appreciable amount of surface 
moisture, another portion of the 100 pounds sample should 
be weighed and spread out in a thin layer on a clean sheet- 
iron plate, and exposed for a period of twenty-four hours to 
the atmosphere of the boiler-room, and by this means air- 
dried. After being weighed again, the percentage which the 
weight shrinks during this drying may be termed the percent- 
age of surface moisture. 

XV. Treatment cf Ashes and Refuse. — The ashes and 
refuse are to be weighed in a dry state. For elaborate trials 
a sample of the same should be procured for analysis. When 
it is desired to know accurately the amount of coal consumed, 
as distinguished from combustible, all lumps of unconsumed 



190 APPENDIX. 

coal one-half inch or more in diameter are to be picked from 
the refuse and deducted from the weight of coal fired. 

XVI. Calorific Tests and Analysis of Coal. — The quality 
of the fuel should be determined either by heat test or by 
analysis, or by both. 

The rational method of determining the total heat of 
combustion is to burn the sample of coal in an atmosphere of 
oxygen-gas, the coal to be sampled as directed in Article XIV 
of this Code. 

The chemical analysis of the coal should be made only by 
an expert chemist. The total heat of combustion computed 
from the results of the ultimate analysis should be obtained 
by the use of Dulong's formula (with constants modified by 
recent determinations), viz., 



14600 C + 62000 



(«-?)• 



in which C, H, and O refer to the proportion of carbon, 
hydrogen, and oxygen respectively, and determined by the 
ultimate analysis.* 

It is recommended that the analysis and the heat test be 
each made by two independent laboratories, and the mean of 
the two results, if there is any difference, be adopted as the 
correct figures. 

It is desirable that a proximate analysis should also be 
made to determine the relative proportions of volatile matter 
and fixed carbon in the coal. 

XVII. Analysis of Flue-gases. — The analysis of the flue- 
gases is an especially valuable method of determining the 
relative value of different methods of firing, or of different 
kinds of furnaces. In making these analyses great care should 

* Favre and Silbermann give 14544 B. T. U. per pound carbon; Berthe- 
lot 14647 B. T. U. Favre and Silbermann give 62032 B. T. U. per pound 
hydrogen; Thomson, 61816 B. T. U. 



APPENDIX. I9 1 

be taken to procure average samples, since the composition 
is apt to vary at different points of the flue ; and where com- 
plete determinations are desired, the analysis should be 
intrusted to an expert chemist. For approximate determina- 
tions the Orsat* or the Hempelf apparatus "may be used by 
the engineer. 

XVIII. Smoke Observations. — It is desirable to have a 
uniform system of determining and recording the quantity of 
smoke produced where bituminous coal is used. The system 
commonly employed is to express the degree of smokiness 
by means of percentages dependent upon the judgment of 
the observer. The Committee does not place much value 
upon a percentage method, because it depends so largely 
upon the personal element, but if this method is used, it is 
desirable that, so far as possible, a definition be given in ex- 
plicit terms as to the basis and method employed in arriving 
at the percentage. 

XIX. Miscellaneous. — In tests for purposes of scientific 
research, in which the determination of all the variables en- 
tering into the test is desired, certain observations should be 
made which are in general unnecessary for ordinary tests. 
These are the measurement of the air-supply, the determina- 
tion of its contained moisture, the determination of the 
amount of heat lost by radiation, of the amount of infiltra- 
tion of air through the setting, and (by condensation of all 
the steam made by the boiler) of the total heat imparted to 
the water. 

As these determinations are not likely to be undertaken 
except by engineers of high scientific attainments, it is* not 
deemed advisable to give directions for making them. 

XX. Calculations of Efficiency. — Two methods of defining 



* See R. S. Hale's paper on " Flue Gas Analysis," Transactions A. S. 
M. £., vol. xviii. p. 901. 

f See Hempel on " Gas Analysis." 



192 APPENDIX. 

and calculating the efficiency of a boiler are recommended. 
They are : 

__ . r , 1 .1 Heat absorbed per lb. combustible 

1. Efficiency of the boiler =^ : , - — ; — - 

H eating value of 1 lb. combustible 

2. Efficiency of the boiler and grate 

_ Heat absorbed per lb. coal 
Heating value of 1 lb. coal 

The first of these is sometimes called the efficiency based 
on combustible, and the second the efficiency based on coal. 
The first is recommended as a standard of comparison for all 
tests, and this is the one which is understood to be referred to 
when the word " efficiency " alone is used without qualifica- 
tion. The second, however, should be included in a report 
of a test, together with the first, whenever the object of the 
test is to determine the efficiency of the boiler and furnace 
together with the grate (or mechanical stoker), or to compare 
different furnaces, grates, fuels, or methods of firing. 

The heat absorbed per pound of combustible (or per pound 
coal) is to be calculated by multiplying the equivalent evapo- 
ration from and at 212 degrees per pound combustible (or 
coal) by 965.7. 

In calculating the efficiency where the coal contains an ap- 
preciable amount of surface moisture, allowance is to be made 
for the heat lost in evaporating this moisture by adding to the 
heat absorbed by the boiler the heat of evaporation thus lost. 
The percentage of surface moisture used in this calculation is 
that which is found in the manner described in Article XIV 
of Code. 

XXI. The Heat-balance. — An approximate "heat-bal- 
ance," or statement of the distribution of the heating value of 
the coal among the several items of heat utilized and heat 
lost may be included in the report of a test when analyses of 
the fuel and of the^chimney gases have been made. It should 
be reported in the following form : 



APPENDIX. 



193 



Heat balance, or Distribution of the Heating Value of the Com- 
bustible. 



Total Heat Value of 1 lb. of Combustible 



... B. T. U. 



5-t 



6. 



Heat absorbed by the boiler = evaporation from and at 
212 degrees per pound of combustible X 965.7. 

Loss due to moisture in coal = per cent of moisture re- 
ferred to combustible -r- 100 X [(212 — t) -f 966 -f 
0.48(7^ — 2i2)](^ = temperature of air in the boiler- 
room, T = that of the flue gases). 

Loss due to moisture formed by the burning of hydrogen 
= per cent of hydrogen to combustible -f- 100 X 
X [(212 - t)+ 966 + 0.48(7' -212)]. 

Loss due to heat carried away in the dry chimney gases = 
weight of gas per pound of combustible X 0.24 X 
(T-t). 

CO 

Loss due to incomplete combustion of carbon = 



X 



per cent C in combustible 



co 2 + co 



B. T. U. 



X 10150. 



Loss due to unconsumed hydrogen and hydrocarbons, to 
heating the moisture in the air, to radiation, and 
unaccounted for. 

Totals ; . * 



Per Cent. 



* The weight of gas per pound of carbon burned may be calculated from the gas analyses 
as follows : 

Dry gas per pound carbon = 2 ~^ Q . ff Q) , in which C0 2 , CO, O, and N are 

the percentages by volume of the several gases. As the sampling and analyses of the gases 
in the present state of the art are liable to considerable errors, the result of this calculation is 
usually only an approximate one. The heat-balance itself is also only approximate for this 
reason, as well as for the fact that it is not possible to determine accurately the percentage 
of unburned hydrogen or hydrocarbons in the flue gases. 

The weight of dry gas per pound of combustible is found by multiplying the dry gas per 
pound of carbon by the percentage of carbon in the combustible, and dividing by 100. 

t C0 2 and CO are respectively the percentage by volume of carbonic acid and carbonic 
oxide in the flue gases. The quantity 10150 = No. heat-units generated by burning to car- 
bonic acid one pound of carbon contained in carbonic oxide. 

XXII. Report of the Trial. — The data and results should 
be reported in the manner given in the following table, omit- 
ting lines where the tests have not been made as elaborately 
as provided for in such table. Additional lines may be added 
for data relating to the specific object of the test. The extra 
lines should be classified under the headings provided in the 



194 APPENDIX. . 

table, and numbered, as per preceding line, with sub letters, 
#, b, etc. 

Data and Results of Evaporative Trials. 

Made by of boiler at to 

determine 

Principal conditions governing the trial 



Kind of fuel 

State of the weather 

i. Date of trial 

2. Duration of trial hours. 

Dimensions and Proportions. 

(A complete description of the boiler should be given on an annexed 
sheet.) 

3. Grate surface width length area sq. ft. 

4. Water-heating surface " 

5. Superheating surface 

6. Ratio of water heating surface to grate surface 

7. Ratio of minimum draft area to grate surface 

Average Pressures. 

8. Steam-pressure by gauge lbs. 

9. Atmospheric pressure by barometer in. 

10. Force of draft between damper and boiler , 

11. Force of draft in furnace 

12. Force of draft in ash-pit 

Average Temperatures. 

13. Of external air deg. 

14. Of fire room . . . . , ,..,.,.. 



15. Of steam 

16. Of feed water entering heater 

17. Of feed water entering economizer. 

18. Of feed water entering boiler 

19. Of escaping gases from boiler 

20. Of escaping gases from economizer. 



APPENDIX. 195 

Fuel. 

21. Size and condition 

22. Weight of wood used in lighting fire lbs. 

23. Weight of coal as fired *., " 

24. Percentage of moisture in coal f _ percent. 

25. Total weight of dry coal consumed (Art. XIV, Code). .... lbs. 

26. Total ash and refuse 

27. Total combustible consumed 

28. Percentage of ash and refuse in dry coal per cent. 

Proximate Analysis of Coal. 

Of Coal. Of Combustible. 

29. Fixed carbon percent. percent. 

30. Volatile matter 

31. Moisture 

32. Ash - 



33. Sulphur, separately determined. 



100 per cent. 100 per cent. 



Ultimate Analysis of Dry Coal. 
(Art. XVI, Code.) 

34. Carbon (C) per cent. 

35. Hydrogen (H). . 

36. Oxygen (O) " 

37. Nitrogen (N) " 

38. Sulphur (S) 



100 per cent. 

39. Moisture in sample of coal as received " 

Analysis of Ash and Refuse. 

40. Carbon per cent. 

41. Earthy matter , " 

Fuel per Hour. 

42. Dry coal consumed per hour lbs. 

43. Combustible consumed per hour •« 

44. Dry coal per square foot of grate surface per hour " 

45. Combustible per square foot of water heating surface per 

hour " 

* Including equivalent of wood used in lighting the fire, not including unburnt coal with- 
drawn from furnace at end of test. One pound of wood is taken to be equal to 0.4 pound of 
coal. 

t This is the total moisture in the coal as found by drying it artificially, as described in Art. 
XIV of Code. 



196 



APPENDIX. 



Calorific Value of Fuel. 

46. Calorific value by oxygen calorimeter, per pound of dry 

coal B. T. U. 

47. Calorific value by oxygen calorimeter, per pound of com- 

bustible " " " 

48. Calorific value by analysis, per lb. of dry coal* 

49. Calorific value by analysis, per pound of combustible 

Quality of Steam. 

50. Percentage of moisture in steam per cent. 

51. Number of degrees of superheating deg. 

52. Quality of steam (dry steam = unity) 

53. Factor of correction for quality of steam (page 119) 

Water. 

54. Total weight of water fed to boiler , lbs. 

55. Water actually evaporated, corrected for quality of steam 

56. Equivalent water evaporated into dry steam from and at 

degrees 

Water per Hour. 

57. Water evaporated per hour, corrected for quality of steam 

58. Equivalent evaporation per hour from and at 212 degrees. 

59. Equivalent evaporation per hour from and at 212 degrees 

per square foot of water-heating surface 

Horse-power. 

60. Horse-power developed. (34! lbs. of water evaporated 

per hour into dry steam from and at 212 degrees, equals 

one horse-power)f H. P. 

61. Builders' rated horse power 

62. Percentage of builders' rated horse-power developed per cent. 

Economic Results. 

63. Water apparently evaporated per lb. of coal under actual 

conditions. (Item 54 -5- Item 23) lbs. 

64. Equivalent evaporation from and at 212 degrees per lb. of 

coal (including moisture) 

65. Equivalent evaporation from and at 212 degrees per lb. of 

dry coal 

66. Equivalent evaporation from and at 212 degrees per lb. of 

combustible 

* See formula for calorific value under Article XVI of Code. 

t Held to be the equivalent of 30 lbs. of water per hour evaporated from 100 degrees Fahr 
into dry steam at 70 lbs. gauge-pressure (See Introduction to Code ) 






APPENDIX. 197 

Efficiency. 
(See Art. XX, Code.) 

67. Efficiency of the boiler ; heat absorbed by the boiler per lb. 

of combustible divided by the heat-value of one lb. of 
combustible.* per cent. 

68. Efficiency of boiler, including the grate ; heat absorbed by 

the boiler, per lb. of dry coal fired, divided by the heat 
value of one lb. of dry coal.f 

Cost of Evaporation. 

69. Cost of coal per ton of 2240 lbs. delivered in boiler-room... $ 

70. Cost of fuel for evaporating 1000 lbs. of water under ob- 

served conditions % 

71. Cost of fuel used for evaporating 1,000 lbs. of water from 

and at 212 degrees % 

Smoke Observations. 

72. Percentage of smoke as observed 

73. Weight of soot per hour obtained from smoke-meter 

74. Volume of soot obtained from smoke-meter per hour 

^In all cases where the word " combustible " is used, it means the coal without moisture 
and ash, but including all other constituents. It is the same as what is called in Europe " coal 
dry and free from ash." 

t The heat value of the coal is to be determined either by an oxygen calorimeter or by cal- 
culation from ultimate analysis. When both methods are used the mean value ii to be taken. 



198 



TABLE J. 



TABLE I.— HEAT OF COMBUSTION OF SUBSTANCES. 



Calories. 

Crystallized carbon toC0 2 .. 7859 

" " to CO... 2405 

Amorphous carbon to CO a . . 8137 

to CO... 2489 

Graphite to C0 2 7901 

Petroleum coke to CO a 8017 

Gas coke to CO a 8047 

Carbon vapor to CO a 8722 

Coal (pure and dry) 7800 to 9000 

Lignite (pure and dry) 6000 to 7000 

Beech charcoal 7 T 40 

Soft charcoal 7071 

Cellulose 4200 

Soft resinous wood 5050 

Hard wood, 4750 

Peat 5940 

Cane sugar 3961 

Asphalt 9532 

Pitch 8400 

Naphthalin 9690 

Paraffin. uooo 

Tallow 9500 

Sulphur 2500 

Petroleum 9600 to 1 1000 

Schist-oil 9000 to 10000 

Heavy coal gas oil 8900 

Cotton oil 9500 

Rape oil 9489 

Olive oil 9473 

Sperm oil 10000 

Hydrogen 34500 

Carbonic oxide 2435 

Marsh gas 13343 

Olefiant gas 12182 

Acetylene 12142 

Carbon vapor (diamond). . . 11134 

Coal gas 4440 to 7370 

Petroleum gas 10800 

Air producer gas 773 to 1370 

Water gas 2350 to 3032 

Mixed gas 1015 to 1548 



B. T. U. 




14146 


Berthelot 


4329 


" 


14647 


" 


4480 


" 


14222 


" 


14503 


Mahler 


14485 


F. &S. 


15700 '• 


Calculated. 


Page 173. 


14040 to 16200 


Various 


10800 to 12600 


" 


12852 


Schwackhofer 


12723 


" 


7560 


Berthelot 


9090 


Gottlieb 


8550 


" 


10692 


Bainbridge 


7I30 


Berthelot 


I7I59 


Slosson &Colburn 


15120 


Anon. 


16842 


Berthelot 


19800 


Mahler 


17100 


Stohmann 


4500 


Berthelot 


17280 to 19800 


Various 


16200 to 18000 


" 


16020 


Ste-Claire Deville 


17100 


Anon. 


17080 


Stohmann 


1 705 1 


<< 


18000 


Gibson 


62100 


Berthelot 


4383 


" 


24017 


<« 


21898 


<( 


21856 


<( 


20041 


<< 


7990 to 12266 


Various 


19440 


Anon. 


1391 to 2466 


Various 


4230 to 5458 


" 


1827 to 2786 


" 



TABLE II. I99 

TABLE II.— THERMOMETER REDUCTION TABLES. 

A. Centigrade to Fahrenheit. 



c. 


F. 


c. 


F. 


C. 


F. 


C. 


F. 


I 


1.8 


10 


18 


100 


180 


1000 


1800 


2 


3-6 


20 


36 


200 


360 


2000 


3600 


3 


5-4 


30 


54 


300 


540 


3000 


5400 


4 


7.2 


40 


72 


400 


720 


4000 


7200 


5 


9.0 


50 


90 


500 


900 


5000 


9000 


6 


10.8 


60 


108 


600 


1080 


6000 


10800 



5 


10 


5f 


100 


55t 


1000 


555f 


1* 


20 


IT i 


200 


m£ 


2000 


iiii£ 


if 


30 


i6f 


300 


i66f 


3000 


i666f 


H 


40 


22| 


400 


222f 


4000 


2222f 


2£ 


5o 


27* 


500 


277| 


5000 


2777f 


3f 


60 


33f 


600 


333f 


6000 


33331 


3t 


70 


38| 


700 


3 88| 


7000 


3 888f 


4t 


80 


44t 


800 


444$ 


8000 


4444f 


5 


90 


50 


900 


500 


9000 


5000 



12.6 70 126 700 1260 7000 12600 

14.4 80 144 800 1440 8000 14400 

16.2 90 162 900 1620 9000 16200 



B. Fahrenheit to Centigrade. 
F. C. F. C. F. C. F. C. 



Having given Centigrade degrees, obtain from Table A the 
corresponding equivalents, and to their sum add 32 . 

Example : Find Fahrenheit degrees corresponding to 
416 C. 

720+ 18 + 10.8 + 32 = 780.8. 

Having given Fahrenheit degrees, subtract 32 ° and find the 
value in Table B corresponding to the remainder. 

Example : Find Centigrade degrees corresponding to 
-i6°F. 

-16-32 = -48, - 4 8°F. = -(22-1 + 4$) = -26$. 



200 



TABLES III, IV, 



TABLE III.— THEORETICAL FLAME TEMPERATURES. 



C to CO 

C to C0 2 

CO to CO a 

Hydrogen 

Marsh gas, CH 4 . . 
Olefiant gas, C 2 H 4 , 
Acetylene, C 2 H 2 . . 

Benzin, CeH 6 

Producer gas , 

Coal gas , 

Petroleum 

Naphthalin 

Wood 

Lignite (dry) 

Coal (bituminous). 
Sulphur to H 2 S0 4 . 



[n Oxygen. 



In Air. 



Centigrade. 


Fahrenheit. 


Centigrade. 


Fahrenheit. 


4265° 


7677° 


1462 


2639° 


I OOOO 


18000 


2718 


4892 


7OIO 


12618 


3000 


5400 


6727 


I2I08 


2674 


4813 


7971 


14348 


2245 


4036 


9659 


17286 


3000 


5400 


1 1 300 


20340 


3400 


6120 


9350 


16830 


2790 


5022 


2500 


4500 


I200 


2160 


5400 


9720 


2700 


4860 


7558 


13604 


24OO 


4320 


9444 


17000 


2730 


4914 


5800 


IO440 


2280 


4104 


3000 


5400 


I200 


2160 


3800 


6840 


1500 


2700 


2300 


4 MO 


IO60 


1908 



TABLE IV.— WEIGHT AND VOLUME OF GASES. 





Weight. 


Volume. 


Name. 


Per Cubic 

Metre in 

Kilograms. 


Per Cubic 
Foot in 
Pounds. 


Per Kilogram 
in Cubic 
Metres. 


Per Pound 

in 
Cubic Feet. 


Air 


I. 29318 
I. 25616 
I.4298 
O.08961 
I.9666 
I- 2515 
I.0727 
O.8047 
2 . 8605 
I. 2519 

0.7I55 
I . I9OO 

' 3.3333 
I- 3415 


O.08073 

0,07845 

O.08926 

O.OO559 

O.12344 

O.07817 

O.06696 

0.05022 

O.1787 

O.07814 

O.O4466 

O.07428 

O.208 

O.08565 


0.773 
O.796 
O.699 
1 1. 160 
O.508 
0.800 
O.932 
I.242 
0.349 
0.799 
1-397 
0.840 
0.303 
0.746 


12.385 
12.763 
11.203 
178.83 

8.147 
I 2 . 800 
I4.930 
I9.9I2 

5.596 
12.797 
22.391 
13.456 

4.808 
II.950 


Nitrogen 






Carbonic acid 

Carbonic oxide 

Carbon vapor 

Aqueous vapor 

Sulphurous acid 

Ethylene, C 2 H 4 

Methane, CH 4 

Acetylene, C 2 H 2 . 

Benzine, C 6 H 6 

Ethane, C 2 H 8 



TABLE V. 



20 1 



A 








ON On 










VO 








NC 


10 


c<- 


in 














VC 






rn 


m 




5 






•SlDtipOJjJ 


on ■* 


co <*■ 


CO 


CO 






u 




oc 


io 


i> 


N 




















m 






<u 




< 
















a 








•*■ 


a 


8 


O 









>\ 




v£ 


co 


oc 




0\ 


°^ « 


t) 


03 




VC 






lO 






— 


.O 




•jiy 


ON •* 


00 


T 


>o 


ci'Z 








a 


•<*• 


h 


VO 


CO 


E 


in 3 


3 






















c 


O 


oc 


8 








-£ S 


s 






nc 


vo 


On t*. 


o> 


ON 







c 

V 


•s;onpoj < j 




CO 


t"» H 




M . 





fcuo 








c 


M 




CO 


11 




>N 























10 CI 


co 

on 10 





00 

10 


(J rt 




>N 
PQ 


•usSAxq 


oc 


ro 


On 00 


ON 


ON 
CO 













c 


10 


N 


w 






\n ir> 


vc 


O 





NO 


a 

_3 








Cn! 


oc 





o^ 


00 




•aiqusnq 


co co 

On 3> 


ON f^ 


On 
CO 


ON 


"O 




-0103 snoasBf) 


c 


6 


c 




^ 





> 












M 
















„ CT 


"O 


^0 


>, 

J3 




•sjonpojj 


<;: 
> u u 


c 




uffi 


8£ 


§ U 






c 


cs 




N 


<N -«• 


N CH 


•2 a 

'en 3 

go 




•uaSXxo 


0' O O 
> * 


c 


O 


O 


O 
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TABLE VI. 



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TABLE VII. 



203 



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204 



TABLE VIII. 



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TABLES IX, X, XI. 



205 



TABLE IX.— TABLE OF SPECIFIC HEAT OF GASEOUS PROD- 
UCTS OF COMBUSTION REFERRED TO THE PROPORTION 
OF CARBONIC ACID. 



Proportion of 
Carbonic Acid 


Specific 
Heat. 


Proportion of 
Carbonic Acid. 


Specific 
Heat. 


5 per 


cent 


.... O.312 


I I 


per 


cent. . 


. O.319 


6 " 


< i 


... O.314 


12 


t i 


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13 


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14 


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15 


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10 " 


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TABLE X.— HEAT OF VAPORIZATION OF WATER AT o° TO 

230 C. 



Temperat 


ure. 


Heat of 


Centigrade. 


Fahrenheit. 


Vaporization 





32 


606.5 


IOO 


212 


537-0 


230 


456 


676.6 



Latent heat of vaporization, 966 (Regnault). 



TABLE XL— SPECIFIC HEAT OF WATER (REGNAULT). 
Temperature. Specific Heat. Temperature. Specific Heat. 



O 1.0000 

10 1.0005 

20 1. 0012 

30 1.0020 

40 I.OO3O 

50 I.OO42 

60 I.OO56 

70 I.OO72 

80 I.OO98 

90 I. OIO9 

100 i. 0130 



no 1-0153 

I20 I. OI77 

I3O I.0204 

I40 I.O232 

I50 1.0262 

l6o I.O294 

170 I.O328 

l80 I.O364 

I9O I. O4OI 

200 I.O44O 



206 



TABLES XIL XIII. 



TABLE XIL— VOLUME OF OXYGEN TO FORM WATER WITH THE 
HYDROGEN OF COAL. 



Per Cent of Hydrogen. 



Oxygen in Litres per 
Kilogram of Coal. 



Oxygen in Cubic Feet 
per Pound of Coal. 



I 55-9 

2 I 12 

3... 168 

4 22 3 

5 2 79 

6 335 

7 39i 

8 446 

9 502 



1.792 
2.699 

3.585 
4.481 

5-397 
6.283 
7.170 
8.096 



TABLE XIIL— QUANTITY OF AIR REQUIRED FOR PERFECT 
COMBUSTION OF FUELS. 



Fuel. 



Coke 

Coal, anthracite 

bituminous . . 

coking 

cannel 

smithy 

Charcoal 

Lignite 

Peat, dry 

Wood, dry 

Petroleum 

Natural gas 

Coal gas 

Water gas 

Producer gas 



Composition. 



Carbon. Hydrogen. Oxygen. Nitrogen 



90.O 

95-4 
87.O 
85.O 
84.O 
O 
o 
o 
o 
o 
o 
7 



77 
90 

7i 
58 
50 
35 
68 
58.0 
34-0 
1 .0 



0.5 
2.2 
5-0 
50 
6.0 
5-o 
2.0 
5.o 
6.0 
6.0 
14.0 
22.5 
23.7 
5-9 
5-o 



1. a 
4.0 
6.0 
8.0 
15.0 



19.0 

30.0 

42.0 

1.0 

1.0 

1.4 
43.0 

21 .O 



0.5 



1.0 



6.2 

3.8 
3.4 

69.0 



Air per- 



Kilogram. Pound 



cu. metres 

IO.O9 

9.OI 

8-93 

8.68 

8.79 
7.67 
8.53 
7.02 

5-75 

4-57 

10.76 

14.20 

14.51 
3.16 

.72 



cu. feet 

162.06 

144.60 

143.40 

139.41 

141.07 

123.15 

133-9° 

II2.43 

92.36 

73-36 

172.86 

227.93 

233.06 

50.70 

II.56 



TABLES XIV y XV. 207 



TABLE XIV.— RELATION BY WEIGHT AND VOLUME OF THE 
COMPONENTS OF AIR. 

Air contains by volume : 

Nitrogen 78.35 

Oxygen 20. J J 

Aqueous vapor o. 84 

Carbonic acid 0.04 

100.00 
Deducting the carbonic acid and aqueous vapor, we have : 
Nitrogen.. ..By volume: 79.04 By weight : 76.83 

Oxygen " " 20.96 " " 23.17 

100.00 100.00 

Ratio of nitrogen to oxygen : 

By volume, — = 3.771. By weight, — = 3.32. 

Ratio of air to oxygen : 

A_ir Air 

By volume, — = 4.771. By weight, _= 4.315. 

Ratio of air to nitrogen : 

Air Air 

By volume, — == 1.265. By weight, — — - = 1.302. 

TABLE XV. -IGNITION POINT OF GASES (Mayer and Munch).* 

Marsh gas, CH 66y° C. 

Ethane, C a H 6 . 616 

Propane, C 3 H i 547 

Acetylene, C 2 H, 580 

Propylene, C S H 6 504 

* Berichte der deutscher Gesellschaft xxvi, 2421. 



FUEL TABLES. 



These tables contain all the available information covering 
the data required which have been published to date. They 
contain analyses of the fuels, and the heat units as determined 
by the authors, whose names tire given. In some cases it has 
been necessary to recalculate the results as published by the 
experimenters to conform with the standard adopted. This 
applies especially to the coals and solid fuels, the data for 
which are given based on pure dry coal, i.e., on the combus- 
tible present. If the actual test of the sample as given is 
desired, it will be easy to make the necessary deductions. 
Some of the cokes and some of the natural gases have been 
calculated, the calculated results being within the limits of 

experimental error in these cases. 

209 



2IO 



FUEL TABLES. 



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212 



FUEL TABLES. 






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242 



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MIXED GAS. 



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248 



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INDEX. 



AGITATOR, BERTHELOT'S, 27 
Aguitton's exp'ments on coal gas, 95 
Air, analysis (table), 207 

necessary for combustion, 125; 

(table), 206 
necessary for combustion 

(table), 201, 202 
used in combustion, 139 
Alexejew's calorimeter, 28 
American Society of Mechanical 
Engineers, boiler-test re- 
port, 177 
Analysis, Cinders, 115 
, Coal, 113 

, should show what, 114 
, Coke, 82 
, Gases, 133 
, Lignite, 78 
, Manchester gas, 93 
, Peat, 80 
, Proximate, 77 
, Waste gases (table), 134, 135 
, Wood, 84 
Andrews' calorimeter, 47 
Anemometer, Fan-wheel, 143 
, Fletcher's, 144 

, Volume of waste gases by, 143 
Apparatus for steam-boiler testing 
should be correct, 183 
, Installation of, 13 
, Hirn's, 145 
, Orsat-Muencke, 134 
Aqueous vapor, Heat of, 159 
Ash, Analysis of, 115 
, Lignite, 78 
, Peat, 80 

, Treatment of, 189 
Aspirator, Oil, 132 
Atomic calorie, 2 
Atwater's calorimeter, 71 

BARRUS'S CALORIMETER, 38 
Berthelot's agitator, 27 
bomb, 48 



Bituminous schist, 79 

Boghead coal, 79 

Boiler-testing. See Steam-boiler 

Testing 
Bomb. See Calorimeter 
Briquettes, how made, 51 
British thermal units, 2 

" to change to 

calories, 3 
Brix's experiments with charcoal, 84 
Bueb-Dessau's experiments on coal 

gas, 95 
Bunsen's researches on flame, 168 
Bunte's experiments on coal, 76 
gas-coke determinations, 9 
experiments on waste gases, 135 
Burnat's smoke tests, 155 

CALCULATION; 

Air necessary for combustion, 125 

Air supplied, 139 

Calories of the boiler test, 159 

Calories of carbon, 54 

Carpenter's calorimeter, 34 

Carbon, 54 

Coal, 66 

Coke, 68 

Colza oil, 64 

Favre and Silbermann's calorim- 
eter, 26 

Flame temperature, 169 

Gases, 67, 94 

Heat units of boiler trial, 159 

Heat units by lead test, 10 

Heat units from chemical com- 
position, 7 

Junker's calorimeter, 41 

Mahler's calorimeter, 61 

" ; abridged, 70 

Regnault and Pfaundler's, 18 

Vapor of carbon, 173 

Volume of waste gases, 143 

Water value of calorimeters, 14, 
63 

24Q 



250 



INDEX. 



Calculation; Weight of waste gases, 

141 
Calories, atomic or molecular, 2 
Kilo-, 3 
Pound-, 2 
To change to B. T. U., 3. See 

Heat Units 
Calorific power, 2 

Ratio of, to fixed carbon, 78 
Calorimeter, Alexejew, 28 
Analytical, 74 
Andrews, 47 
Atwater, 71 
Barrus, 38 
Berthelot, 48 

corrections, 53 

examples, 54 

operation, 53 
Carpenter's, 31 

calculation, 34 
Constant pressure, 20 
Constant volume, 45 
Constant pressure and volume, 

ratio of, 45 
Correction for F. and S., 16 

Berthelot, 53 

cooling, 18, 60 

Junker's, 42 

Regnault and Pfaundler's, 18 
Cost of, 27 
Dulong, 20 

Evaluation in water. See Calo- 
rimeter, Water value 
Favre and Silbermann, 21 

Calculation, 26 

in complete combustion with, 
23. 25 
Fischer, 29 
Hartley, 40 
Junker, 40 

calculation, 41 

errors, 42 
Kroeker, 73 
Mahler, 57 

and Berthelot compared, 70 

calculation, 61 
, abridged, 70 

enamel chips off, 58 (foot-note) 

examples, 64 

for gases, 62 

operation, 59 
Protection for, 13 
Rumford, 20 
Schwackhofer, 35 

waste gases, 37 
Thompson, L., 43 
Thompson, W., 37 



Calorimeter, Thomsen, 30 
Throttling, 117 
Walther-Hempel, 74 
Water value 

, Berthelot's calorimeter, 14 
by combustion, 14 
by mixing, 15 

Favre and Silbermann's cal- 
orimeter, 14 
Fischer's calorimeter, 30 
Lord and Haas' calorimeter, 14 
Mahler's calorimeter, 14, 63 
Witz, 47 
Calorimeters, 12 
Calorimetric endiometer, 47 
Candle power and heat of combus- 
tion compared, 96 
Cannel coal, 79 

Carbon, calculation of calories, 54 
calories by various authors, 12 
in cinders, 115 
" smoke, 154 

" " ; analysis of, 154, 191 
oxygen necessary for, 125 
vapor, weight, and calories, 173 
Carpenter's calorimeter, 31 
Carbonic acid, Automatic determi- 
nation of, 147, 148, 150 
in producer gases. See Gas 

Producer 
in waste gases, 81, 84, 91, 134, 

137, 155 
, proper proportion in waste 
gases, 135 
Carbonic oxide, Flame temperature 
of, 170 
in producer gas, 99 
in waste gases, 84, 91, 101, 134, 
137 (table 135), 164 
Cellulose, calories of, 85 
Charbon roux % 83 
Charcoal, peat, 80 
wood, 83 

; Brix's tests, 84 
, half-burnt, 83 
; Sauvage's tests, 83 
; Scheurer-K.'s results, 84 
, Waste gases of, 84 
Cinder, Analysis of, 115 
Coal, Actual evaporation of, 76 
, Air necessary, 126 
, " supplied, 139 
Analysis, 113; (tables), 209-230 

should show, 114 
Bunte's experiments, 76 
Calories of, 66 
Difference in samples of, 113 



INDEX. 



2 5 I 



Coal, Gruner's table, 77 

Heat of combustion (table), 198, 

209 
Johnson's tests, 75 
Moisture in, 112, 114, 188 
Morin and Tresca's tests, 75 
Pure, 75 

Ratio of calories and fixed car- 
bon, 77 
Ratio of hyd'gen and carbon, 78 
Sampling, 112 
Size for combustion, 24 
Uniformity in same bed, 112 
Weight of, in 
Coal gas. See Gas, Coal 
Coke analyses (table), 209 
Calories of, 68 
Composition of, 82 
Heat of combustion (table), 230 
Kinds of, 81 
Use of, 82 
Colza oil, Calories of, 64 
Combustion, Air necessary, 125 
Air supplied, 139 
Heat of. See Heat of Combus- 
tion 
incomplete in F. and S. calorim- 
eter, 23 
Constant pressure, 20, 45 
" volume, 45 
" - relation of, to 

constant pressure, 45 
Cooling, Newton's law, 60 

Regnault-Pfaundler's law, 18 
Corrections for Berthelot calorim- 
eter, 53 
Cooling, 18, 60 
Junker calorimeter, 42 

DASYMETER, t 4 6 

Differential gauge, Segur's, 145 

Dissociation, effect of, upon tem- 
perature, 168 

Dulong's calorimeter, 20 

Dulong's formula, 7 

, Agreement of, with test, 9 - 
, Mahler's limit to, 10 (foot-note) 
heat unit, 21 

ECONOMETER, 148 
Efficiency of steam-boilers, 191 
Electric igniter, Heat of, 70 
Evaluation in water. See Water 

Value 
Evaporative effect of coal, 76 

, Factor for, 174 

power of fuel, 174 



Evaporative power of charcoal, 84 
" gas, 93 
" " lignite, 79 
" " peat, 80 
" " wood, 86 
Evaporative power petroleum, 90 
of natural gas, J07 
unit, 180 
Examples, Berthelot's cal'meter, 54 
Carpenter's calorimeter, 34 
Favre and S. " 26 

Mahler's " 64 

FAN-WHEEL ANEMOMETER.I43 
Favre and S.'s calorimeter, 21 
Fischer's calorimeter, 29 
Flame, 168 

Bunsen's researches, 168 
length, 169 

not due to incandescence, 168 
not due to solid particles, 168 
Propagation of, 168 
temperature, Calculation of, 169 
, Loss due to dissociation, 168 
acetylene, 170 
bor-methyl, 168 
carbon and carbonic oxide, 170 
hydrogen, 169 

marsh and defiant gases, 171 
oils, 172 
petroleum, 172 

producer and other gases, 171 
solid fuels, 172 
table, 200 
Fletcher's anemometer, 144 
Flue-gas. See Waste Gases 
Formula, Balling's, 8 
Burnat's, 143 
Dulong's, 7 
German Engineers', 8 
Hirn's, 146 
Jacobus's, 143 
Mahler's, 9 
Quality of steam, 119 
Regnault, for vaporization, 4 
Regnault and Pfaundler's, 18 
Schwackhofer's, 8 
Superheated steam, 123 
Throttling calorimeter, 122 
Vaporization of water, 4 
Waste gases, weight, 141, 143 
Welter's, 10 
Fuel, Air required for, 125; table, 
206 
Air supplied to, 139 
Calorific power under steam- 
boiler, 109 



252 



INDEX. 



Fuel, Evaporative power, 174 

Gaseous, 92 

Weight of, in 
Fuels, 1 

, Division of, I 

Tables, 209 

GAS, COAL 

Aguitton's experiments, 95 
Bueb-Dessau's experiments, 95 
Heat of combustion (table), 243 
Mahler's experiments, 96 
Variation in, 95 
Gas-composimeter, 150 
Gas, gasogene ; heat theory, 97 
Loss of calories, 98 
Value, 97 
Varieties, 98 
Gas-holder, Oil, 132 
Gas, Natural. See Natural Gas 
Gas, Producer ; Heat theory of, 99 
Heat of combustion (table)245,246 
Mahler's experiments, 101 
Gas sampler, A. S. M. E., 131 

Scheurer-Kestner's, 128 
Gas, water. See Water Gas 
Gaseous fuels, 92 

Heat of combustion of (tables), 245 
Gases, Analysis, 133 
as fuel, 92 

Calculation of calories, 67 
Comparative value, 107 
Heat of combustion from anal- 
ysis, 93 
Heat units, 164; table, 203 

" example, 165 
Ignition point (table), 207 
Weight and volume (table), 200 
Specific heat (table), 204 
Gases, waste. See Waste Gases 

Specific heat of (table), 205 
Gottlieb's wood tests, 86 
Gruener's coal table, 77 

HARTLEY'S CALORIMETER, 40 
Heat, balance in boiler trials, 193 
Loss of, in producer gas, 104 
of aqueous vapor, 159 
combination, 94 
combustible gases, 164 
combustion, 3 

and candle power, 96 
; Calculated vs. det'mined, 9 
Cause of disagreement, 10 
Determination of, 3, 4 
From chem. composition, 7 
, Litharge or lead test, 10 



Heat, Methods of determining, 7 
of carbon, 12, 54 
carbon vapor, 173 
coal, 66 
coke, 68 
colza oil, 64 
constant pressure, 20 
constant pressure and vol- 
ume, 45 
fuels (tables), 209 
gas, 67 

gases, calculation, 68, 93 
gases, difference in, 94 
gases, modified by con- 
densation, 94 
gases (table), 203, 241 et 

seq. 
hydrogen, 97 
marsh gas, 97 
natural gas, 106; table, 241 
oils (table), 238 
defiant gas, 97 
petroleum, 90 
various subst. (table), 198 
electric igniter, 70 
hygroscopic water, 162 
sensible of the temperature, 160 
soot, 166 
vaporization of water, 4; table, 

205 
water of combustion, 162 
Specific ; gases (table), 204 
waste gases (table), 205 
water (table), 205 
Heat units, Dulong's, 21 

from chemical composition, 7 
lead reduction test, 10 
Ratio of, to fixed carbon, 77 
of steam-boiler tests, Cal'tion, 159 
of steam-boiler tests Distribu- 
tion, 167 
Heat value, 2 

of fuels (tables), 209 
Heating by charcoal, 84 
coke, 82 
gas, 92 
lignite, 78 
oil, 89, 90 
j>eat, 80 
wood, 84 
Hirn's waste-gas apparatus, 145 

formula, 146 
Horse-power, Commercial, 180 
Hydrocarbons, Unconsumed, 25 
Hydrogen, Calories of, 4 
in cinders, 115 
, Oxygen necessary for, 125 



INDEX. 



253 



IGNITER, ELECTRIC 

Heat of, 70 
Ignition point of gases (table), 207 
Incandescence not flame, 168 
Indiana natural gas analyses, 105 
Installation of apparatus, 13 

JACOBUS'S FORMULA, 143 
Johnson's coal tests, 75 
Junker's calorimeter, 40 

KENT ON WASTE GASES, 141 
Kent's ratio of hydrogen and carbon 

in coal, 78 
revision of Johnson's tests, 75 
Kilo-calorie, 3 
Kroeker calorimeter and correction 

for water, 73 

LEAD OR LITHARGE TEST, 10 
is unreliable, 11 

Lignite, 78 

, Heat of combustion (table), 231 

Lord and Haas on Ohio and Penn- 
sylvania coal, 9 

Luminosity, 168 

depends on pressure, 169 
not due to solid particles, 168 

MAHLER'S CALORIMETER, 57 
determinations of gas, 101 
experiments on coal gas, 96 
formula, 9 

Manchester gas, Analysis of, 93 

Mixed gas, 101 

, Calories of (table), 245 

Moisture in coal, 112, 114 

Moisture in steam, 119, 187 

Molecular calorie, 2 

Morin and Tresca on coal, 75 

Morin and Tresca's wood tests, 86 

NAPHTHALIN, CALORIES OF.46 

Natural gas and analysis of, 105 
Calories of, 106; (table), 241 
Value of, 106 
Variation in, 105 
Nitrogen, ratio of, to oxygen 

(table), 207 
Nixon's coal ; calories of, deter- 
mined, 66 

OHIO NATURAL GAS, 105 
Oil aspirator or gas-holder, 132 
Oils, Heat of combustion (table), 238 
Orsat-Muenckefapparatus, 134 



Oven cokes, Heat of combustion 

(table), 234 
Oxygen, Compressed, is dry, 52 
in cylinders, 59 
necessary for combustion, 125 

" (table), 

201, 202 
, Ratio of, to nitrogen in air 

(table), 207 
required to form water with coal, 

140 ; (table), 206 
To prepare, 24 

PASTILLES, HOW MADE, 51 
Peat, 80 

; Calories of (table), 232 
Petroleum, 88 

at Chicago, Canada, Moscow, 89 

, Calorific power of, 90 

heating tests, 90 

, Calories of (tables), 238 

, Steam used in atomizing, 91 
Pittsburg natural gas, 105 
Pneumatic pyrometer, 152 
Pound-calorie, 2 

Producer gas, 98. See Gas, Producer 
Products of combustion of 

Alexejew's calorimeter, 28 

charcoal, 84 

Favre and Silbermann's calorim- 
eter, 26 

oil, 91 

Schwackhofer's calorimeter, 37. 
See Waste Gases. 
Pyrometer, Pneumatic, 152 

REGNAULT'S FORMULA, 4 
Regnault and Pfaundler's law, 18 
Ringelmann's smoke scale, 158 
Ronchamp coal, Smoke of, 156 

" Waste gases of, 134 
Rothkohle, 83 
Rumford's calorimeter, 20 

SAMPLER, GAS, 128, 131 
Sampling, Coal, 112 
Sauvage's exp'ments on charcoal, 83 
Scheurer-Kestner's experiments on 
charcoal, 84 

gas sampler, 128 

smoke analysis, 155 

and Meunier-Dollfus on coal, 75 
Schist, Bituminous, 79 
Schwackhofer's calorimeter, 35 
Segur's differential gauge, 145 
Sensitiveness of thermometers,. 6 
Shale oil, 88 



254 



INDEX. 



Smoke, Bunte's observations, 157 
Burnat's experiments, 155 
Carbon in, 154 
Ringelmann's scale, 158 
Scheurer-Kestner's analysis, 155 
Tatlock's tests, 155 
Soda-lime for absorbing moisture, 23 
Soot, Heat units of, 166 
Specific heat. See Heat, Specific 
" " of water not consid- 

ered, 3 
Steam, Moisture in, 117, 119, 187 
, Quality of, 119, 187 
, Superheated, 123 
, Temperature of, 116 
used in atomizing petroleum, 91 
Steam-boilers, petroleum-fired, 89 

, Lignite-fired, 79 
Steam-boiler testing 

apparatus to be correct, 183 
Ashes and residues, 189 
Analysis of cinders, 115 
" " coal, 113 

" " waste gases, 133, 
190 
Boiler and chimney to be 

heated. 183 
Calculation of air necessary, 125 
" " supplied, 139 
" " heat units, 159 

" waste gases, 136, 
141, 146 
Carbon in smoke, 154 
Coal used, 182 

Corrections of apparatus, 183 
determine what, 109 
Distribution of calories, 167 

" " heat, 109 

Duration of test, 115 
Early tests, 109 
Efficiency, 191 

Examination of boiler, etc., 182 
Heat balance. 192 
Heat tests and coal anal., 190 
Johnson's tests, 109 
Keeping records, 186 
Moisture in steam, 117 
Need of knowledge of cal- 
ories in, 109 
Preliminaries of, 181 
Quality of steam, 119, 187 
Report of A. S. M. E. com- 
mittee, 177 
Report of trial, 193 
Sampling the coal, -112 
Scheurer-Kestner's tests, no 
Starting and stopping, 184 



Steam-boiler testing, Temperature 
of steam, 116 
Temperatureof waste gases, 151 
Volume of air necessary, 125 
" " " supplied, 139 
" " waste gases, 127 
Waste gas samples and an- 
alysis, 133, 190 
Water evaporated, 116 
Weight of fuel, in 

" " waste gases, 141 
What is necesary, no 
Sulphur, oxygen necessary for, 126 

TABLE ; AIR COMPONENTS, 207 
Air for combustion, 201, 202 
" for perfect combustion, 206 
Ash analyses, 115 
Candle power and heat of com- 
bustion, 96 
Coal (Gruner's), 77 
Coke analyses, 82 
Distribution of calories, 167 
Flame temperatures, 200 
Fuels, 209 
Heat balance, 193 
Heat of combustion, 198 
" " " of fuels, 209 

" " " " gases, 202 

" " lignites, 231 
" " " " peat, 232 

" " " " wood, 86, 233 

" " vapor'n of water, 205 
Ignition point of gases, 207 
Natural gas, 105, 106, 241, 242 
Oxygen for combustion, 201, 202 
Oxygen to form water, 206 
Regnault and Pfaundler's law, 18 
Ronchamp coal waste gases, 134 
Smoke analyses, 157 
Specific heat of gases, 204 

•' " waste gases, 205 
" " water, 205 
Thermometer reduction, 199 
Waste gas analyses, 134, 135 
Water value calculation, 15 
Weight and volume of gases, 200 
Wood, 86 
Tatlock's smoke tests, 155 
Temperature, Heat of sensible, 160 

of waste gases, 151 
Thermal units, 2 
Thermometer, 4 

, Correction, mercury column, 6 
, Favre and Silbermann's, 6 
, Metastatic, 6 
, reduction table, 199 



INDEX. 



255 



Thermometer, Sensibility of, 6 
Thomsen's calorimeter, 30 
Thompson's, L., calorimeter, 43 
Thompson's, W., 37 

Throttling calorimeter, 117 



UNIT OF EVAPORATION, 179 
Units of heat, 3 

VAPORIZATION OF WATER, 4 

Vaporization of water (table), 205 
Variation in coal gas, 95 

" natural gas, 105 



WALTHER-HEMPEL 

Calorimeter, 74 
Waste gas analysis, 190 
Waste gases, Automatic apparatus 
for, 147 
, Bunte's results, 135 
from charcoal, 84 
" petroleum, 91 
" Ronchamp coal, 134 
, Heat of, 160 
, Hirn's apparatus, 145 

" formula, 146 
, Schwackhofer's calorimeter, 37 



Waste gases (table), 134, 135 
, Temperature of, 151 
Volume of, 127 
Water evaporated, 116 

, Heat of combination, 162 

, Heat of vaporization of, 4; 

table, 205 
, Hygroscopic, heat of, 162 
in Lignite, 78 
in peat, 80 
, Kroeker's correction for, 73 
, Specific heat (table), 205 
, Specific heat of, not considered, 3 
-value of cal'meters, 14, 15, 30, 63 
Water gas, 101 

, Heat of combustion of (table), 

245 et seq. 
Theory, 102 
Loss of heat, 104 
Weight of carbon vapor, 173 
fuel, in 
waste gases, 141 
Witz calorimeter, 47 
Wood, Condition for burning, 87 
Gottlieb's tests, 86 
Calories (table), 86, 233 
Hydrate of carbon, 84 
Morin and Tresca's tests, 86 
Wood charcoal. See Charcoal Wood. 






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